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 $91.41   4.216%   $95.2638   $95.26   $95.25   $95.30  
  Purchase #2 $115.90   8.448%   $125.6912   $125.69   $125.70   $125.70  
  Purchase #3 $94.83   8.199%   $102.6051   $102.61   $102.60   $102.60  
  Purchase #4 $248.67   5.771%   $263.0207   $263.02   $263.00   $263.00  
  Purchase #5 $197.67   13.355%   $224.0688   $224.07   $224.05   $224.10  
  Purchase #6 $92.82   5.796%   $98.1998   $98.20   $98.20   $98.20  
  Purchase #7 $233.92   5.122%   $245.9014   $245.90   $245.90   $245.90  
  7 purchase totals = $1,075.22       $1,154.7508   $1,154.75   $1,154.70   $1,154.80