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 $118.79   5.418%   $125.226   $125.23   $125.25   $125.20  
  Purchase #2 $210.55   3.224%   $217.3381   $217.34   $217.35   $217.30  
  Purchase #3 $174.45   5.305%   $183.7046   $183.70   $183.70   $183.70  
  Purchase #4 $227.78   12.274%   $255.7377   $255.74   $255.75   $255.70  
  Purchase #5 $158.41   6.297%   $168.3851   $168.39   $168.40   $168.40  
  Purchase #6 $53.72   4.764%   $56.2792   $56.28   $56.30   $56.30  
  Purchase #7 $32.76   5.394%   $34.5271   $34.53   $34.55   $34.50  
  7 purchase totals = $976.46       $1,041.1978   $1,041.21   $1,041.30   $1,041.10