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 $60.62   3.433%   $62.7011   $62.70   $62.70   $62.70  
  Purchase #2 $147.44   13.243%   $166.9655   $166.97   $166.95   $167.00  
  Purchase #3 $84.44   4.671%   $88.3842   $88.38   $88.40   $88.40  
  Purchase #4 $82.54   12.390%   $92.7667   $92.77   $92.75   $92.80  
  Purchase #5 $132.26   8.109%   $142.985   $142.99   $143.00   $143.00  
  Purchase #6 $69.54   9.469%   $76.1247   $76.12   $76.10   $76.10  
  Purchase #7 $218.67   11.606%   $244.0488   $244.05   $244.05   $244.00  
  7 purchase totals = $795.51       $873.9760   $873.98   $873.95   $874.00