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 $108.60   4.722%   $113.7281   $113.73   $113.75   $113.70  
  Purchase #2 $52.82   3.550%   $54.6951   $54.70   $54.70   $54.70  
  Purchase #3 $229.67   3.485%   $237.674   $237.67   $237.65   $237.70  
  Purchase #4 $90.72   4.408%   $94.7189   $94.72   $94.70   $94.70  
  Purchase #5 $88.47   7.257%   $94.8903   $94.89   $94.90   $94.90  
  Purchase #6 $119.83   5.456%   $126.3679   $126.37   $126.35   $126.40  
  Purchase #7 $31.44   5.616%   $33.2057   $33.21   $33.20   $33.20  
  7 purchase totals = $721.55       $755.2800   $755.29   $755.25   $755.30