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 $86.82   10.513%   $95.9474   $95.95   $95.95   $95.90  
  Purchase #2 $41.39   5.794%   $43.7881   $43.79   $43.80   $43.80  
  Purchase #3 $61.61   5.141%   $64.7774   $64.78   $64.80   $64.80  
  Purchase #4 $217.56   9.393%   $237.9954   $238.00   $238.00   $238.00  
  Purchase #5 $139.82   8.313%   $151.4432   $151.44   $151.45   $151.40  
  Purchase #6 $93.69   4.505%   $97.9107   $97.91   $97.90   $97.90  
  Purchase #7 $95.75   11.191%   $106.4654   $106.47   $106.45   $106.50  
  7 purchase totals = $736.64       $798.3276   $798.34   $798.35   $798.30