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 $228.53   7.103%   $244.7625   $244.76   $244.75   $244.80  
  Purchase #2 $162.69   8.594%   $176.6716   $176.67   $176.65   $176.70  
  Purchase #3 $43.78   6.856%   $46.7816   $46.78   $46.80   $46.80  
  Purchase #4 $214.58   5.739%   $226.8947   $226.89   $226.90   $226.90  
  Purchase #5 $244.30   9.298%   $267.015   $267.02   $267.00   $267.00  
  Purchase #6 $100.35   10.222%   $110.6078   $110.61   $110.60   $110.60  
  Purchase #7 $107.70   3.348%   $111.3058   $111.31   $111.30   $111.30  
  7 purchase totals = $1,101.93       $1,184.0390   $1,184.04   $1,184.00   $1,184.10