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 $68.63   6.578%   $73.1445   $73.14   $73.15   $73.10  
  Purchase #2 $36.61   8.562%   $39.7445   $39.74   $39.75   $39.70  
  Purchase #3 $71.71   6.683%   $76.5024   $76.50   $76.50   $76.50  
  Purchase #4 $117.59   7.192%   $126.0471   $126.05   $126.05   $126.00  
  Purchase #5 $186.46   4.665%   $195.1584   $195.16   $195.15   $195.20  
  Purchase #6 $200.61   13.708%   $228.1096   $228.11   $228.10   $228.10  
  Purchase #7 $200.33   4.517%   $209.3789   $209.38   $209.40   $209.40  
  7 purchase totals = $881.94       $948.0854   $948.08   $948.10   $948.00