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 $181.62   8.243%   $196.5909   $196.59   $196.60   $196.60  
  Purchase #2 $192.57   7.746%   $207.4865   $207.49   $207.50   $207.50  
  Purchase #3 $247.86   11.448%   $276.235   $276.24   $276.25   $276.20  
  Purchase #4 $37.95   9.110%   $41.4072   $41.41   $41.40   $41.40  
  Purchase #5 $198.65   3.442%   $205.4875   $205.49   $205.50   $205.50  
  Purchase #6 $42.69   13.644%   $48.5146   $48.51   $48.50   $48.50  
  Purchase #7 $186.89   7.717%   $201.3123   $201.31   $201.30   $201.30  
  7 purchase totals = $1,088.23       $1,177.0340   $1,177.04   $1,177.05   $1,177.00