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 $57.40   9.674%   $62.9529   $62.95   $62.95   $63.00  
  Purchase #2 $134.49   12.590%   $151.4223   $151.42   $151.40   $151.40  
  Purchase #3 $61.59   9.854%   $67.6591   $67.66   $67.65   $67.70  
  Purchase #4 $24.38   9.125%   $26.6047   $26.60   $26.60   $26.60  
  Purchase #5 $40.43   11.208%   $44.9614   $44.96   $44.95   $45.00  
  Purchase #6 $206.71   8.843%   $224.9894   $224.99   $225.00   $225.00  
  Purchase #7 $163.74   10.792%   $181.4108   $181.41   $181.40   $181.40  
  7 purchase totals = $688.74       $760.0006   $759.99   $759.95   $760.10