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 $208.52   3.416%   $215.643   $215.64   $215.65   $215.60  
  Purchase #2 $98.43   6.873%   $105.1951   $105.20   $105.20   $105.20  
  Purchase #3 $171.77   8.654%   $186.635   $186.64   $186.65   $186.60  
  Purchase #4 $73.30   12.827%   $82.7022   $82.70   $82.70   $82.70  
  Purchase #5 $116.90   6.636%   $124.6575   $124.66   $124.65   $124.70  
  Purchase #6 $53.49   12.792%   $60.3324   $60.33   $60.35   $60.30  
  Purchase #7 $14.32   10.708%   $15.8534   $15.85   $15.85   $15.90  
  7 purchase totals = $736.73       $791.0186   $791.02   $791.05   $791.00