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 $244.76   7.185%   $262.346   $262.35   $262.35   $262.30  
  Purchase #2 $60.97   7.809%   $65.7311   $65.73   $65.75   $65.70  
  Purchase #3 $9.87   3.483%   $10.2138   $10.21   $10.20   $10.20  
  Purchase #4 $216.63   8.175%   $234.3395   $234.34   $234.35   $234.30  
  Purchase #5 $237.34   4.328%   $247.6121   $247.61   $247.60   $247.60  
  Purchase #6 $7.64   8.827%   $8.3144   $8.31   $8.30   $8.30  
  Purchase #7 $209.44   3.179%   $216.0981   $216.10   $216.10   $216.10  
  7 purchase totals = $986.65       $1,044.6550   $1,044.65   $1,044.65   $1,044.50