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 $111.80   11.766%   $124.9544   $124.95   $124.95   $125.00  
  Purchase #2 $157.53   4.526%   $164.6598   $164.66   $164.65   $164.70  
  Purchase #3 $58.98   10.524%   $65.1871   $65.19   $65.20   $65.20  
  Purchase #4 $173.57   6.257%   $184.4303   $184.43   $184.45   $184.40  
  Purchase #5 $149.94   4.251%   $156.3139   $156.31   $156.30   $156.30  
  Purchase #6 $59.82   4.729%   $62.6489   $62.65   $62.65   $62.60  
  Purchase #7 $184.49   5.519%   $194.672   $194.67   $194.65   $194.70  
  7 purchase totals = $896.13       $952.8664   $952.86   $952.85   $952.90