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 $67.40   10.723%   $74.6273   $74.63   $74.65   $74.60  
  Purchase #2 $103.89   4.791%   $108.8674   $108.87   $108.85   $108.90  
  Purchase #3 $44.62   5.309%   $46.9889   $46.99   $47.00   $47.00  
  Purchase #4 $52.36   12.567%   $58.9401   $58.94   $58.95   $58.90  
  Purchase #5 $244.43   7.849%   $263.6153   $263.62   $263.60   $263.60  
  Purchase #6 $135.28   7.856%   $145.9076   $145.91   $145.90   $145.90  
  Purchase #7 $230.51   9.841%   $253.1945   $253.19   $253.20   $253.20  
  7 purchase totals = $878.49       $952.1411   $952.15   $952.15   $952.10