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 $222.53   6.753%   $237.5575   $237.56   $237.55   $237.60  
  Purchase #2 $245.63   9.256%   $268.3655   $268.37   $268.35   $268.40  
  Purchase #3 $95.93   13.527%   $108.9065   $108.91   $108.90   $108.90  
  Purchase #4 $119.57   3.699%   $123.9929   $123.99   $124.00   $124.00  
  Purchase #5 $126.71   8.518%   $137.5032   $137.50   $137.50   $137.50  
  Purchase #6 $197.46   3.420%   $204.2131   $204.21   $204.20   $204.20  
  Purchase #7 $101.86   9.614%   $111.6528   $111.65   $111.65   $111.70  
  7 purchase totals = $1,109.69       $1,192.1915   $1,192.19   $1,192.15   $1,192.30