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 $62.84   3.692%   $65.1601   $65.16   $65.15   $65.20  
  Purchase #2 $206.86   8.221%   $223.866   $223.87   $223.85   $223.90  
  Purchase #3 $207.97   4.152%   $216.6049   $216.60   $216.60   $216.60  
  Purchase #4 $16.64   11.310%   $18.522   $18.52   $18.50   $18.50  
  Purchase #5 $163.68   7.771%   $176.3996   $176.40   $176.40   $176.40  
  Purchase #6 $91.42   6.500%   $97.3623   $97.36   $97.35   $97.40  
  Purchase #7 $161.53   10.567%   $178.5989   $178.60   $178.60   $178.60  
  7 purchase totals = $910.94       $976.5138   $976.51   $976.45   $976.60