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 $176.38   9.413%   $192.9826   $192.98   $193.00   $193.00  
  Purchase #2 $194.37   7.362%   $208.6795   $208.68   $208.70   $208.70  
  Purchase #3 $45.97   8.328%   $49.7984   $49.80   $49.80   $49.80  
  Purchase #4 $175.63   11.519%   $195.8608   $195.86   $195.85   $195.90  
  Purchase #5 $134.27   6.105%   $142.4672   $142.47   $142.45   $142.50  
  Purchase #6 $196.45   5.398%   $207.0544   $207.05   $207.05   $207.10  
  Purchase #7 $44.46   8.412%   $48.2   $48.20   $48.20   $48.20  
  7 purchase totals = $967.53       $1,045.0429   $1,045.04   $1,045.05   $1,045.20