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 $58.61   12.826%   $66.1273   $66.13   $66.15   $66.10  
  Purchase #2 $116.82   8.456%   $126.6983   $126.70   $126.70   $126.70  
  Purchase #3 $73.95   5.499%   $78.0165   $78.02   $78.00   $78.00  
  Purchase #4 $220.96   3.769%   $229.288   $229.29   $229.30   $229.30  
  Purchase #5 $208.77   9.526%   $228.6574   $228.66   $228.65   $228.70  
  Purchase #6 $207.28   8.594%   $225.0936   $225.09   $225.10   $225.10  
  Purchase #7 $48.68   9.807%   $53.454   $53.45   $53.45   $53.50  
  7 purchase totals = $935.07       $1,007.3351   $1,007.34   $1,007.35   $1,007.40