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 $85.75   11.433%   $95.5538   $95.55   $95.55   $95.60  
  Purchase #2 $196.38   12.403%   $220.737   $220.74   $220.75   $220.70  
  Purchase #3 $21.93   11.479%   $24.4473   $24.45   $24.45   $24.40  
  Purchase #4 $71.90   7.185%   $77.066   $77.07   $77.05   $77.10  
  Purchase #5 $103.90   10.725%   $115.0433   $115.04   $115.05   $115.00  
  Purchase #6 $124.80   5.199%   $131.2884   $131.29   $131.30   $131.30  
  Purchase #7 $100.63   11.756%   $112.4601   $112.46   $112.45   $112.50  
  7 purchase totals = $705.29       $776.5959   $776.60   $776.60   $776.60