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 $233.61   5.167%   $245.6806   $245.68   $245.70   $245.70  
  Purchase #2 $93.51   4.468%   $97.688   $97.69   $97.70   $97.70  
  Purchase #3 $53.34   9.808%   $58.5716   $58.57   $58.55   $58.60  
  Purchase #4 $221.80   12.480%   $249.4806   $249.48   $249.50   $249.50  
  Purchase #5 $74.27   5.308%   $78.2123   $78.21   $78.20   $78.20  
  Purchase #6 $249.96   5.616%   $263.9978   $264.00   $264.00   $264.00  
  Purchase #7 $219.82   11.288%   $244.6333   $244.63   $244.65   $244.60  
  7 purchase totals = $1,146.31       $1,238.2642   $1,238.26   $1,238.30   $1,238.30