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 $88.44   7.468%   $95.0447   $95.04   $95.05   $95.00  
  Purchase #2 $36.83   4.266%   $38.4012   $38.40   $38.40   $38.40  
  Purchase #3 $166.71   4.663%   $174.4837   $174.48   $174.50   $174.50  
  Purchase #4 $200.57   7.823%   $216.2606   $216.26   $216.25   $216.30  
  Purchase #5 $9.71   7.661%   $10.4539   $10.45   $10.45   $10.50  
  Purchase #6 $214.84   6.792%   $229.4319   $229.43   $229.45   $229.40  
  Purchase #7 $208.72   7.392%   $224.1486   $224.15   $224.15   $224.10  
  7 purchase totals = $925.82       $988.2246   $988.21   $988.25   $988.20