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 $178.90   12.523%   $201.3036   $201.30   $201.30   $201.30  
  Purchase #2 $217.30   5.645%   $229.5666   $229.57   $229.55   $229.60  
  Purchase #3 $153.89   12.814%   $173.6095   $173.61   $173.60   $173.60  
  Purchase #4 $68.53   3.470%   $70.908   $70.91   $70.90   $70.90  
  Purchase #5 $195.44   13.832%   $222.4733   $222.47   $222.45   $222.50  
  Purchase #6 $28.26   5.268%   $29.7487   $29.75   $29.75   $29.70  
  Purchase #7 $172.63   13.508%   $195.9489   $195.95   $195.95   $195.90  
  7 purchase totals = $1,014.95       $1,123.5586   $1,123.56   $1,123.50   $1,123.50