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 $60.38   5.200%   $63.5198   $63.52   $63.50   $63.50  
  Purchase #2 $215.64   10.275%   $237.797   $237.80   $237.80   $237.80  
  Purchase #3 $86.30   9.166%   $94.2103   $94.21   $94.20   $94.20  
  Purchase #4 $91.94   3.602%   $95.2517   $95.25   $95.25   $95.30  
  Purchase #5 $13.82   7.409%   $14.8439   $14.84   $14.85   $14.80  
  Purchase #6 $239.54   13.741%   $272.4552   $272.46   $272.45   $272.50  
  Purchase #7 $85.54   7.842%   $92.248   $92.25   $92.25   $92.20  
  7 purchase totals = $793.16       $870.3259   $870.33   $870.30   $870.30