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 $44.27   4.451%   $46.2405   $46.24   $46.25   $46.20  
  Purchase #2 $63.84   10.434%   $70.5011   $70.50   $70.50   $70.50  
  Purchase #3 $83.40   3.844%   $86.6059   $86.61   $86.60   $86.60  
  Purchase #4 $97.84   10.554%   $108.166   $108.17   $108.15   $108.20  
  Purchase #5 $220.95   10.102%   $243.2704   $243.27   $243.25   $243.30  
  Purchase #6 $92.42   5.143%   $97.1732   $97.17   $97.15   $97.20  
  Purchase #7 $102.63   12.144%   $115.0934   $115.09   $115.10   $115.10  
  7 purchase totals = $705.35       $767.0505   $767.05   $767.00   $767.10