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 $72.49   4.298%   $75.6056   $75.61   $75.60   $75.60  
  Purchase #2 $174.83   11.668%   $195.2292   $195.23   $195.25   $195.20  
  Purchase #3 $236.48   9.861%   $259.7993   $259.80   $259.80   $259.80  
  Purchase #4 $162.55   3.739%   $168.6277   $168.63   $168.65   $168.60  
  Purchase #5 $245.42   9.153%   $267.8833   $267.88   $267.90   $267.90  
  Purchase #6 $117.83   3.730%   $122.2251   $122.23   $122.25   $122.20  
  Purchase #7 $104.44   10.658%   $115.5712   $115.57   $115.55   $115.60  
  7 purchase totals = $1,114.04       $1,204.9414   $1,204.95   $1,205.00   $1,204.90