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 $187.93   4.158%   $195.7441   $195.74   $195.75   $195.70  
  Purchase #2 $53.26   10.324%   $58.7586   $58.76   $58.75   $58.80  
  Purchase #3 $176.29   13.270%   $199.6837   $199.68   $199.70   $199.70  
  Purchase #4 $155.97   3.356%   $161.2044   $161.20   $161.20   $161.20  
  Purchase #5 $208.82   3.148%   $215.3937   $215.39   $215.40   $215.40  
  Purchase #6 $227.30   5.252%   $239.2378   $239.24   $239.25   $239.20  
  Purchase #7 $179.82   6.519%   $191.5425   $191.54   $191.55   $191.50  
  7 purchase totals = $1,189.39       $1,261.5648   $1,261.55   $1,261.60   $1,261.50