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 $94.27   8.169%   $101.9709   $101.97   $101.95   $102.00  
  Purchase #2 $12.38   8.650%   $13.4509   $13.45   $13.45   $13.50  
  Purchase #3 $233.89   4.764%   $245.0325   $245.03   $245.05   $245.00  
  Purchase #4 $220.63   11.848%   $246.7702   $246.77   $246.75   $246.80  
  Purchase #5 $79.50   6.727%   $84.848   $84.85   $84.85   $84.80  
  Purchase #6 $176.57   5.289%   $185.9088   $185.91   $185.90   $185.90  
  Purchase #7 $44.95   8.102%   $48.5918   $48.59   $48.60   $48.60  
  7 purchase totals = $862.19       $926.5731   $926.57   $926.55   $926.60