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 $119.30   5.260%   $125.5752   $125.58   $125.60   $125.60  
  Purchase #2 $32.76   4.535%   $34.2457   $34.25   $34.25   $34.20  
  Purchase #3 $226.62   5.207%   $238.4201   $238.42   $238.40   $238.40  
  Purchase #4 $156.53   6.348%   $166.4665   $166.47   $166.45   $166.50  
  Purchase #5 $57.63   6.602%   $61.4347   $61.43   $61.45   $61.40  
  Purchase #6 $22.40   7.845%   $24.1573   $24.16   $24.15   $24.20  
  Purchase #7 $230.82   8.827%   $251.1945   $251.19   $251.20   $251.20  
  7 purchase totals = $846.06       $901.4940   $901.50   $901.50   $901.50