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 $104.36   7.664%   $112.3582   $112.36   $112.35   $112.40  
  Purchase #2 $165.67   5.642%   $175.0171   $175.02   $175.00   $175.00  
  Purchase #3 $143.56   7.251%   $153.9695   $153.97   $153.95   $154.00  
  Purchase #4 $222.94   11.531%   $248.6472   $248.65   $248.65   $248.60  
  Purchase #5 $60.54   9.764%   $66.4511   $66.45   $66.45   $66.50  
  Purchase #6 $202.76   3.596%   $210.0512   $210.05   $210.05   $210.10  
  Purchase #7 $217.81   7.818%   $234.8384   $234.84   $234.85   $234.80  
  7 purchase totals = $1,117.64       $1,201.3327   $1,201.34   $1,201.30   $1,201.40