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 $97.26   7.435%   $104.4913   $104.49   $104.50   $104.50  
  Purchase #2 $57.89   7.733%   $62.3666   $62.37   $62.35   $62.40  
  Purchase #3 $58.27   8.545%   $63.2492   $63.25   $63.25   $63.20  
  Purchase #4 $120.78   3.449%   $124.9457   $124.95   $124.95   $124.90  
  Purchase #5 $224.60   4.256%   $234.159   $234.16   $234.15   $234.20  
  Purchase #6 $8.36   4.362%   $8.7247   $8.72   $8.70   $8.70  
  Purchase #7 $116.78   10.406%   $128.9321   $128.93   $128.95   $128.90  
  7 purchase totals = $683.94       $726.8686   $726.87   $726.85   $726.80