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 $86.74   6.735%   $92.5819   $92.58   $92.60   $92.60  
  Purchase #2 $242.89   3.173%   $250.5969   $250.60   $250.60   $250.60  
  Purchase #3 $46.36   11.747%   $51.8059   $51.81   $51.80   $51.80  
  Purchase #4 $182.37   5.410%   $192.2362   $192.24   $192.25   $192.20  
  Purchase #5 $82.81   7.534%   $89.0489   $89.05   $89.05   $89.00  
  Purchase #6 $176.44   10.143%   $194.3363   $194.34   $194.35   $194.30  
  Purchase #7 $79.97   3.206%   $82.5338   $82.53   $82.55   $82.50  
  7 purchase totals = $897.58       $953.1399   $953.15   $953.20   $953.00