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 $43.91   4.870%   $46.0484   $46.05   $46.05   $46.00  
  Purchase #2 $158.92   11.167%   $176.6666   $176.67   $176.65   $176.70  
  Purchase #3 $84.45   9.455%   $92.4347   $92.43   $92.45   $92.40  
  Purchase #4 $214.46   7.428%   $230.3901   $230.39   $230.40   $230.40  
  Purchase #5 $38.71   11.867%   $43.3037   $43.30   $43.30   $43.30  
  Purchase #6 $116.96   6.715%   $124.8139   $124.81   $124.80   $124.80  
  Purchase #7 $8.50   9.630%   $9.3186   $9.32   $9.30   $9.30  
  7 purchase totals = $665.91       $722.9760   $722.97   $722.95   $722.90