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 $174.41   12.283%   $195.8328   $195.83   $195.85   $195.80  
  Purchase #2 $240.54   10.678%   $266.2249   $266.22   $266.20   $266.20  
  Purchase #3 $181.66   5.136%   $190.9901   $190.99   $191.00   $191.00  
  Purchase #4 $89.79   5.156%   $94.4196   $94.42   $94.40   $94.40  
  Purchase #5 $114.74   4.373%   $119.7576   $119.76   $119.75   $119.80  
  Purchase #6 $213.42   13.332%   $241.8732   $241.87   $241.85   $241.90  
  Purchase #7 $232.62   8.804%   $253.0999   $253.10   $253.10   $253.10  
  7 purchase totals = $1,247.18       $1,362.1981   $1,362.19   $1,362.15   $1,362.20