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 $88.69   5.249%   $93.3453   $93.35   $93.35   $93.30  
  Purchase #2 $226.89   3.706%   $235.2985   $235.30   $235.30   $235.30  
  Purchase #3 $36.66   9.285%   $40.0639   $40.06   $40.05   $40.10  
  Purchase #4 $48.59   6.702%   $51.8465   $51.85   $51.85   $51.80  
  Purchase #5 $168.56   4.208%   $175.653   $175.65   $175.65   $175.70  
  Purchase #6 $100.42   10.810%   $111.2754   $111.28   $111.30   $111.30  
  Purchase #7 $225.69   4.770%   $236.4554   $236.46   $236.45   $236.50  
  7 purchase totals = $895.50       $943.9380   $943.95   $943.95   $944.00