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 $40.43   11.160%   $44.942   $44.94   $44.95   $44.90  
  Purchase #2 $116.62   6.422%   $124.1093   $124.11   $124.10   $124.10  
  Purchase #3 $183.73   9.391%   $200.9841   $200.98   $201.00   $201.00  
  Purchase #4 $212.39   10.165%   $233.9794   $233.98   $234.00   $234.00  
  Purchase #5 $103.73   4.338%   $108.2298   $108.23   $108.25   $108.20  
  Purchase #6 $164.32   7.133%   $176.0409   $176.04   $176.05   $176.00  
  Purchase #7 $57.83   12.155%   $64.8592   $64.86   $64.85   $64.90  
  7 purchase totals = $879.05       $953.1447   $953.14   $953.20   $953.10