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 $238.27   8.377%   $258.2299   $258.23   $258.25   $258.20  
  Purchase #2 $225.56   7.244%   $241.8996   $241.90   $241.90   $241.90  
  Purchase #3 $19.51   12.748%   $21.9971   $22.00   $22.00   $22.00  
  Purchase #4 $190.37   7.310%   $204.286   $204.29   $204.30   $204.30  
  Purchase #5 $217.71   4.299%   $227.0694   $227.07   $227.05   $227.10  
  Purchase #6 $155.37   7.803%   $167.4935   $167.49   $167.50   $167.50  
  Purchase #7 $58.66   5.703%   $62.0054   $62.01   $62.00   $62.00  
  7 purchase totals = $1,105.45       $1,182.9809   $1,182.99   $1,183.00   $1,183.00