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 $44.44   9.406%   $48.62   $48.62   $48.60   $48.60  
  Purchase #2 $9.92   6.722%   $10.5868   $10.59   $10.60   $10.60  
  Purchase #3 $228.95   3.175%   $236.2192   $236.22   $236.20   $236.20  
  Purchase #4 $58.62   3.732%   $60.8077   $60.81   $60.80   $60.80  
  Purchase #5 $126.48   5.521%   $133.463   $133.46   $133.45   $133.50  
  Purchase #6 $60.34   10.238%   $66.5176   $66.52   $66.50   $66.50  
  Purchase #7 $62.86   9.541%   $68.8575   $68.86   $68.85   $68.90  
  7 purchase totals = $591.61       $625.0718   $625.08   $625.00   $625.10