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 $232.27   6.592%   $247.5812   $247.58   $247.60   $247.60  
  Purchase #2 $206.97   13.290%   $234.4763   $234.48   $234.50   $234.50  
  Purchase #3 $66.76   6.594%   $71.1622   $71.16   $71.15   $71.20  
  Purchase #4 $47.54   3.656%   $49.2781   $49.28   $49.30   $49.30  
  Purchase #5 $19.52   10.504%   $21.5704   $21.57   $21.55   $21.60  
  Purchase #6 $15.73   3.179%   $16.2301   $16.23   $16.25   $16.20  
  Purchase #7 $84.60   8.608%   $91.8824   $91.88   $91.90   $91.90  
  7 purchase totals = $673.39       $732.1807   $732.18   $732.25   $732.30