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 $238.76   9.864%   $262.3113   $262.31   $262.30   $262.30  
  Purchase #2 $241.96   6.531%   $257.7624   $257.76   $257.75   $257.80  
  Purchase #3 $32.25   8.855%   $35.1057   $35.11   $35.10   $35.10  
  Purchase #4 $211.39   7.358%   $226.9441   $226.94   $226.95   $226.90  
  Purchase #5 $196.89   12.451%   $221.4048   $221.40   $221.40   $221.40  
  Purchase #6 $12.56   12.719%   $14.1575   $14.16   $14.15   $14.20  
  Purchase #7 $93.54   6.144%   $99.2871   $99.29   $99.30   $99.30  
  7 purchase totals = $1,027.35       $1,116.9729   $1,116.97   $1,116.95   $1,117.00