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 $112.42   5.211%   $118.2782   $118.28   $118.30   $118.30  
  Purchase #2 $216.34   10.782%   $239.6658   $239.67   $239.65   $239.70  
  Purchase #3 $113.34   13.482%   $128.6205   $128.62   $128.60   $128.60  
  Purchase #4 $178.53   11.494%   $199.0502   $199.05   $199.05   $199.10  
  Purchase #5 $61.76   3.530%   $63.9401   $63.94   $63.95   $63.90  
  Purchase #6 $136.49   11.833%   $152.6409   $152.64   $152.65   $152.60  
  Purchase #7 $51.60   3.177%   $53.2393   $53.24   $53.25   $53.20  
  7 purchase totals = $870.48       $955.4350   $955.44   $955.45   $955.40