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 $238.58   5.716%   $252.2172   $252.22   $252.20   $252.20  
  Purchase #2 $213.68   9.322%   $233.5992   $233.60   $233.60   $233.60  
  Purchase #3 $54.82   11.147%   $60.9308   $60.93   $60.95   $60.90  
  Purchase #4 $34.70   11.420%   $38.6627   $38.66   $38.65   $38.70  
  Purchase #5 $59.42   10.660%   $65.7542   $65.75   $65.75   $65.80  
  Purchase #6 $52.79   3.565%   $54.672   $54.67   $54.65   $54.70  
  Purchase #7 $46.67   6.240%   $49.5822   $49.58   $49.60   $49.60  
  7 purchase totals = $700.66       $755.4183   $755.41   $755.40   $755.50