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 $93.31   5.274%   $98.2312   $98.23   $98.25   $98.20  
  Purchase #2 $185.54   4.601%   $194.0767   $194.08   $194.10   $194.10  
  Purchase #3 $248.72   7.245%   $266.7398   $266.74   $266.75   $266.70  
  Purchase #4 $129.46   7.841%   $139.611   $139.61   $139.60   $139.60  
  Purchase #5 $81.80   12.425%   $91.9637   $91.96   $91.95   $92.00  
  Purchase #6 $50.56   8.483%   $54.849   $54.85   $54.85   $54.80  
  Purchase #7 $187.70   10.496%   $207.401   $207.40   $207.40   $207.40  
  7 purchase totals = $977.09       $1,052.8724   $1,052.87   $1,052.90   $1,052.80