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 $195.53   3.364%   $202.1076   $202.11   $202.10   $202.10  
  Purchase #2 $226.62   5.178%   $238.3544   $238.35   $238.35   $238.40  
  Purchase #3 $49.75   12.354%   $55.8961   $55.90   $55.90   $55.90  
  Purchase #4 $242.38   4.285%   $252.766   $252.77   $252.75   $252.80  
  Purchase #5 $152.78   9.258%   $166.9244   $166.92   $166.90   $166.90  
  Purchase #6 $156.82   3.262%   $161.9355   $161.94   $161.95   $161.90  
  Purchase #7 $98.69   10.347%   $108.9015   $108.90   $108.90   $108.90  
  7 purchase totals = $1,122.57       $1,186.8855   $1,186.89   $1,186.85   $1,186.90