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 $214.79   13.820%   $244.474   $244.47   $244.45   $244.50  
  Purchase #2 $206.65   10.686%   $228.7326   $228.73   $228.75   $228.70  
  Purchase #3 $46.95   10.643%   $51.9469   $51.95   $51.95   $51.90  
  Purchase #4 $231.67   9.662%   $254.054   $254.05   $254.05   $254.10  
  Purchase #5 $72.77   13.418%   $82.5343   $82.53   $82.55   $82.50  
  Purchase #6 $230.34   13.731%   $261.968   $261.97   $261.95   $262.00  
  Purchase #7 $17.96   13.383%   $20.3636   $20.36   $20.35   $20.40  
  7 purchase totals = $1,021.13       $1,144.0734   $1,144.06   $1,144.05   $1,144.10