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 $67.81   10.833%   $75.1559   $75.16   $75.15   $75.20  
  Purchase #2 $142.41   13.162%   $161.154   $161.15   $161.15   $161.20  
  Purchase #3 $52.29   9.576%   $57.2973   $57.30   $57.30   $57.30  
  Purchase #4 $10.53   6.516%   $11.2161   $11.22   $11.20   $11.20  
  Purchase #5 $224.63   6.821%   $239.952   $239.95   $239.95   $240.00  
  Purchase #6 $198.31   8.260%   $214.6904   $214.69   $214.70   $214.70  
  Purchase #7 $197.68   3.438%   $204.4762   $204.48   $204.50   $204.50  
  7 purchase totals = $893.66       $963.9419   $963.95   $963.95   $964.10