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 $60.32   3.782%   $62.6013   $62.60   $62.60   $62.60  
  Purchase #2 $229.86   10.144%   $253.177   $253.18   $253.20   $253.20  
  Purchase #3 $140.78   5.760%   $148.8889   $148.89   $148.90   $148.90  
  Purchase #4 $207.26   3.636%   $214.796   $214.80   $214.80   $214.80  
  Purchase #5 $46.42   5.326%   $48.8923   $48.89   $48.90   $48.90  
  Purchase #6 $91.64   11.349%   $102.0402   $102.04   $102.05   $102.00  
  Purchase #7 $41.93   11.481%   $46.744   $46.74   $46.75   $46.70  
  7 purchase totals = $818.21       $877.1397   $877.14   $877.20   $877.10