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 $59.86   5.661%   $63.2487   $63.25   $63.25   $63.20  
  Purchase #2 $159.43   9.356%   $174.3463   $174.35   $174.35   $174.30  
  Purchase #3 $63.99   3.653%   $66.3276   $66.33   $66.35   $66.30  
  Purchase #4 $130.77   9.697%   $143.4508   $143.45   $143.45   $143.50  
  Purchase #5 $109.74   11.811%   $122.7014   $122.70   $122.70   $122.70  
  Purchase #6 $13.70   9.815%   $15.0447   $15.04   $15.05   $15.00  
  Purchase #7 $192.64   6.222%   $204.6261   $204.63   $204.65   $204.60  
  7 purchase totals = $730.13       $789.7456   $789.75   $789.80   $789.60