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 $33.76   4.287%   $35.2073   $35.21   $35.20   $35.20  
  Purchase #2 $222.66   5.842%   $235.6678   $235.67   $235.65   $235.70  
  Purchase #3 $71.30   8.378%   $77.2735   $77.27   $77.25   $77.30  
  Purchase #4 $206.95   6.715%   $220.8467   $220.85   $220.85   $220.80  
  Purchase #5 $25.39   10.138%   $27.964   $27.96   $27.95   $28.00  
  Purchase #6 $15.30   7.458%   $16.4411   $16.44   $16.45   $16.40  
  Purchase #7 $99.27   4.807%   $104.0419   $104.04   $104.05   $104.00  
  7 purchase totals = $674.63       $717.4423   $717.44   $717.40   $717.40