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 $48.33   3.332%   $49.9404   $49.94   $49.95   $49.90  
  Purchase #2 $244.98   12.811%   $276.3644   $276.36   $276.35   $276.40  
  Purchase #3 $210.36   12.771%   $237.2251   $237.23   $237.25   $237.20  
  Purchase #4 $248.78   10.187%   $274.1232   $274.12   $274.10   $274.10  
  Purchase #5 $173.63   4.633%   $181.6743   $181.67   $181.65   $181.70  
  Purchase #6 $217.74   8.637%   $236.5462   $236.55   $236.55   $236.50  
  Purchase #7 $188.95   3.528%   $195.6162   $195.62   $195.60   $195.60  
  7 purchase totals = $1,332.77       $1,451.4898   $1,451.49   $1,451.45   $1,451.40