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 $243.58   7.552%   $261.9752   $261.98   $262.00   $262.00  
  Purchase #2 $172.96   10.358%   $190.8752   $190.88   $190.90   $190.90  
  Purchase #3 $214.72   4.614%   $224.6272   $224.63   $224.65   $224.60  
  Purchase #4 $58.45   9.345%   $63.9122   $63.91   $63.90   $63.90  
  Purchase #5 $187.25   8.586%   $203.3273   $203.33   $203.35   $203.30  
  Purchase #6 $143.36   13.319%   $162.4541   $162.45   $162.45   $162.50  
  Purchase #7 $154.92   3.592%   $160.4847   $160.48   $160.50   $160.50  
  7 purchase totals = $1,175.24       $1,267.6559   $1,267.66   $1,267.75   $1,267.70