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 $181.60   7.855%   $195.8647   $195.86   $195.85   $195.90  
  Purchase #2 $48.57   11.109%   $53.9656   $53.97   $53.95   $54.00  
  Purchase #3 $85.48   11.406%   $95.2298   $95.23   $95.25   $95.20  
  Purchase #4 $112.91   5.609%   $119.2431   $119.24   $119.25   $119.20  
  Purchase #5 $229.90   8.485%   $249.407   $249.41   $249.40   $249.40  
  Purchase #6 $106.38   7.475%   $114.3319   $114.33   $114.35   $114.30  
  Purchase #7 $107.43   11.832%   $120.1411   $120.14   $120.15   $120.10  
  7 purchase totals = $872.27       $948.1832   $948.18   $948.20   $948.10