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 $57.55   8.331%   $62.3445   $62.34   $62.35   $62.30  
  Purchase #2 $214.74   6.732%   $229.1963   $229.20   $229.20   $229.20  
  Purchase #3 $206.55   4.706%   $216.2702   $216.27   $216.25   $216.30  
  Purchase #4 $111.54   4.748%   $116.8359   $116.84   $116.85   $116.80  
  Purchase #5 $10.53   9.733%   $11.5549   $11.55   $11.55   $11.60  
  Purchase #6 $224.46   5.400%   $236.5808   $236.58   $236.60   $236.60  
  Purchase #7 $85.61   11.708%   $95.6332   $95.63   $95.65   $95.60  
  7 purchase totals = $910.98       $968.4158   $968.41   $968.45   $968.40