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 $94.26   4.372%   $98.381   $98.38   $98.40   $98.40  
  Purchase #2 $33.87   7.508%   $36.413   $36.41   $36.40   $36.40  
  Purchase #3 $32.52   10.642%   $35.9808   $35.98   $36.00   $36.00  
  Purchase #4 $207.71   10.491%   $229.5009   $229.50   $229.50   $229.50  
  Purchase #5 $196.84   5.433%   $207.5343   $207.53   $207.55   $207.50  
  Purchase #6 $101.79   10.798%   $112.7813   $112.78   $112.80   $112.80  
  Purchase #7 $31.44   12.297%   $35.3062   $35.31   $35.30   $35.30  
  7 purchase totals = $698.43       $755.8975   $755.89   $755.95   $755.90