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 $62.34   4.853%   $65.3654   $65.37   $65.35   $65.40  
  Purchase #2 $162.48   13.663%   $184.6796   $184.68   $184.70   $184.70  
  Purchase #3 $112.39   7.295%   $120.5889   $120.59   $120.60   $120.60  
  Purchase #4 $66.71   6.662%   $71.1542   $71.15   $71.15   $71.20  
  Purchase #5 $177.39   11.315%   $197.4617   $197.46   $197.45   $197.50  
  Purchase #6 $136.55   11.528%   $152.2915   $152.29   $152.30   $152.30  
  Purchase #7 $145.92   7.690%   $157.1412   $157.14   $157.15   $157.10  
  7 purchase totals = $863.78       $948.6825   $948.68   $948.70   $948.80