Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $186.51   10.288%   $205.6981   $205.70   $205.70   $205.70  
  Purchase #2 $230.80   13.534%   $262.0365   $262.04   $262.05   $262.00  
  Purchase #3 $163.95   10.759%   $181.5894   $181.59   $181.60   $181.60  
  Purchase #4 $175.42   11.480%   $195.5582   $195.56   $195.55   $195.60  
  Purchase #5 $247.72   5.693%   $261.8227   $261.82   $261.80   $261.80  
  Purchase #6 $245.26   12.776%   $276.5944   $276.59   $276.60   $276.60  
  Purchase #7 $205.33   12.525%   $231.0476   $231.05   $231.05   $231.00  
  7 purchase totals = $1,454.99       $1,614.3469   $1,614.35   $1,614.35   $1,614.30