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 $96.69   6.251%   $102.7341   $102.73   $102.75   $102.70  
  Purchase #2 $96.33   4.601%   $100.7621   $100.76   $100.75   $100.80  
  Purchase #3 $192.77   8.230%   $208.635   $208.64   $208.65   $208.60  
  Purchase #4 $93.70   3.833%   $97.2915   $97.29   $97.30   $97.30  
  Purchase #5 $246.92   6.795%   $263.6982   $263.70   $263.70   $263.70  
  Purchase #6 $98.42   4.786%   $103.1304   $103.13   $103.15   $103.10  
  Purchase #7 $155.44   11.398%   $173.1571   $173.16   $173.15   $173.20  
  7 purchase totals = $980.27       $1,049.4084   $1,049.41   $1,049.45   $1,049.40