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 $13.68   5.851%   $14.4804   $14.48   $14.50   $14.50  
  Purchase #2 $59.40   4.307%   $61.9584   $61.96   $61.95   $62.00  
  Purchase #3 $221.55   6.789%   $236.591   $236.59   $236.60   $236.60  
  Purchase #4 $197.52   12.368%   $221.9493   $221.95   $221.95   $221.90  
  Purchase #5 $55.31   3.584%   $57.2923   $57.29   $57.30   $57.30  
  Purchase #6 $238.83   7.567%   $256.9023   $256.90   $256.90   $256.90  
  Purchase #7 $224.25   5.569%   $236.7385   $236.74   $236.75   $236.70  
  7 purchase totals = $1,010.54       $1,085.9122   $1,085.91   $1,085.95   $1,085.90