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 $204.75   4.758%   $214.492   $214.49   $214.50   $214.50  
  Purchase #2 $161.99   7.194%   $173.6436   $173.64   $173.65   $173.60  
  Purchase #3 $221.62   10.529%   $244.9544   $244.95   $244.95   $245.00  
  Purchase #4 $142.48   9.824%   $156.4772   $156.48   $156.50   $156.50  
  Purchase #5 $188.77   4.808%   $197.8461   $197.85   $197.85   $197.80  
  Purchase #6 $163.74   4.720%   $171.4685   $171.47   $171.45   $171.50  
  Purchase #7 $245.73   11.557%   $274.129   $274.13   $274.15   $274.10  
  7 purchase totals = $1,329.08       $1,433.0108   $1,433.01   $1,433.05   $1,433.00