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 $59.25   3.627%   $61.399   $61.40   $61.40   $61.40  
  Purchase #2 $194.95   11.692%   $217.7436   $217.74   $217.75   $217.70  
  Purchase #3 $16.57   7.693%   $17.8447   $17.84   $17.85   $17.80  
  Purchase #4 $162.97   6.315%   $173.2616   $173.26   $173.25   $173.30  
  Purchase #5 $229.68   6.177%   $243.8673   $243.87   $243.85   $243.90  
  Purchase #6 $24.26   12.770%   $27.358   $27.36   $27.35   $27.40  
  Purchase #7 $186.98   4.505%   $195.4034   $195.40   $195.40   $195.40  
  7 purchase totals = $874.66       $936.8776   $936.87   $936.85   $936.90