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 $68.28   11.267%   $75.9731   $75.97   $75.95   $76.00  
  Purchase #2 $101.97   12.804%   $115.0262   $115.03   $115.05   $115.00  
  Purchase #3 $68.79   13.663%   $78.1888   $78.19   $78.20   $78.20  
  Purchase #4 $201.39   5.147%   $211.7555   $211.76   $211.75   $211.80  
  Purchase #5 $21.89   6.787%   $23.3757   $23.38   $23.40   $23.40  
  Purchase #6 $124.37   9.176%   $135.7822   $135.78   $135.80   $135.80  
  Purchase #7 $68.59   6.319%   $72.9242   $72.92   $72.90   $72.90  
  7 purchase totals = $655.28       $713.0257   $713.03   $713.05   $713.10