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 $226.42   6.722%   $241.64   $241.64   $241.65   $241.60  
  Purchase #2 $134.61   13.520%   $152.8093   $152.81   $152.80   $152.80  
  Purchase #3 $172.73   5.870%   $182.8693   $182.87   $182.85   $182.90  
  Purchase #4 $44.79   8.839%   $48.749   $48.75   $48.75   $48.70  
  Purchase #5 $158.83   3.153%   $163.8379   $163.84   $163.85   $163.80  
  Purchase #6 $245.68   10.542%   $271.5796   $271.58   $271.60   $271.60  
  Purchase #7 $216.77   10.844%   $240.2765   $240.28   $240.30   $240.30  
  7 purchase totals = $1,199.83       $1,301.7616   $1,301.77   $1,301.80   $1,301.70