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 $59.94   4.713%   $62.765   $62.77   $62.75   $62.80  
  Purchase #2 $21.68   8.382%   $23.4972   $23.50   $23.50   $23.50  
  Purchase #3 $32.66   4.521%   $34.1366   $34.14   $34.15   $34.10  
  Purchase #4 $76.69   13.357%   $86.9335   $86.93   $86.95   $86.90  
  Purchase #5 $236.89   4.447%   $247.4245   $247.42   $247.40   $247.40  
  Purchase #6 $89.61   10.682%   $99.1821   $99.18   $99.20   $99.20  
  Purchase #7 $221.85   7.613%   $238.7394   $238.74   $238.75   $238.70  
  7 purchase totals = $739.32       $792.6783   $792.68   $792.70   $792.60