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 $212.98   13.577%   $241.8963   $241.90   $241.90   $241.90  
  Purchase #2 $249.84   8.471%   $271.0039   $271.00   $271.00   $271.00  
  Purchase #3 $194.36   13.500%   $220.5986   $220.60   $220.60   $220.60  
  Purchase #4 $97.56   8.539%   $105.8906   $105.89   $105.90   $105.90  
  Purchase #5 $59.83   3.549%   $61.9534   $61.95   $61.95   $62.00  
  Purchase #6 $78.75   10.720%   $87.192   $87.19   $87.20   $87.20  
  Purchase #7 $203.27   7.313%   $218.1351   $218.14   $218.15   $218.10  
  7 purchase totals = $1,096.59       $1,206.6699   $1,206.67   $1,206.70   $1,206.70