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 $59.29   5.468%   $62.532   $62.53   $62.55   $62.50  
  Purchase #2 $32.73   10.656%   $36.2177   $36.22   $36.20   $36.20  
  Purchase #3 $70.92   5.825%   $75.0511   $75.05   $75.05   $75.10  
  Purchase #4 $153.91   4.418%   $160.7097   $160.71   $160.70   $160.70  
  Purchase #5 $20.77   13.805%   $23.6373   $23.64   $23.65   $23.60  
  Purchase #6 $205.69   13.239%   $232.9213   $232.92   $232.90   $232.90  
  Purchase #7 $101.68   8.768%   $110.5953   $110.60   $110.60   $110.60  
  7 purchase totals = $644.99       $701.6644   $701.67   $701.65   $701.60