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 $219.33   11.453%   $244.4499   $244.45   $244.45   $244.40  
  Purchase #2 $27.98   6.308%   $29.745   $29.75   $29.75   $29.70  
  Purchase #3 $58.79   8.476%   $63.773   $63.77   $63.75   $63.80  
  Purchase #4 $193.94   6.734%   $206.9999   $207.00   $207.00   $207.00  
  Purchase #5 $163.63   11.404%   $182.2904   $182.29   $182.30   $182.30  
  Purchase #6 $179.84   9.485%   $196.8978   $196.90   $196.90   $196.90  
  Purchase #7 $141.92   3.462%   $146.8333   $146.83   $146.85   $146.80  
  7 purchase totals = $985.43       $1,070.9893   $1,070.99   $1,071.00   $1,070.90