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 $214.98   10.686%   $237.9528   $237.95   $237.95   $238.00  
  Purchase #2 $53.63   12.414%   $60.2876   $60.29   $60.30   $60.30  
  Purchase #3 $125.43   13.149%   $141.9228   $141.92   $141.90   $141.90  
  Purchase #4 $116.70   10.521%   $128.978   $128.98   $129.00   $129.00  
  Purchase #5 $9.45   12.581%   $10.6389   $10.64   $10.65   $10.60  
  Purchase #6 $203.52   6.331%   $216.4049   $216.40   $216.40   $216.40  
  Purchase #7 $81.48   5.802%   $86.2075   $86.21   $86.20   $86.20  
  7 purchase totals = $805.19       $882.3925   $882.39   $882.40   $882.40