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 $204.39   5.116%   $214.8466   $214.85   $214.85   $214.80  
  Purchase #2 $60.77   3.645%   $62.9851   $62.99   $63.00   $63.00  
  Purchase #3 $41.82   13.342%   $47.3996   $47.40   $47.40   $47.40  
  Purchase #4 $232.66   5.185%   $244.7234   $244.72   $244.70   $244.70  
  Purchase #5 $208.99   13.368%   $236.9278   $236.93   $236.95   $236.90  
  Purchase #6 $207.95   8.560%   $225.7505   $225.75   $225.75   $225.80  
  Purchase #7 $184.91   4.558%   $193.3382   $193.34   $193.35   $193.30  
  7 purchase totals = $1,141.49       $1,225.9712   $1,225.98   $1,226.00   $1,225.90