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 $87.43   8.305%   $94.6911   $94.69   $94.70   $94.70  
  Purchase #2 $91.31   11.139%   $101.481   $101.48   $101.50   $101.50  
  Purchase #3 $87.38   6.775%   $93.3   $93.30   $93.30   $93.30  
  Purchase #4 $122.90   13.828%   $139.8946   $139.89   $139.90   $139.90  
  Purchase #5 $29.74   13.552%   $33.7704   $33.77   $33.75   $33.80  
  Purchase #6 $146.82   13.712%   $166.952   $166.95   $166.95   $167.00  
  Purchase #7 $245.62   7.850%   $264.9012   $264.90   $264.90   $264.90  
  7 purchase totals = $811.20       $894.9903   $894.98   $895.00   $895.10