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 $86.95   13.323%   $98.5343   $98.53   $98.55   $98.50  
  Purchase #2 $15.47   4.197%   $16.1193   $16.12   $16.10   $16.10  
  Purchase #3 $188.98   4.275%   $197.0589   $197.06   $197.05   $197.10  
  Purchase #4 $103.25   11.168%   $114.781   $114.78   $114.80   $114.80  
  Purchase #5 $64.58   13.734%   $73.4494   $73.45   $73.45   $73.40  
  Purchase #6 $104.71   12.519%   $117.8186   $117.82   $117.80   $117.80  
  Purchase #7 $208.62   3.631%   $216.195   $216.20   $216.20   $216.20  
  7 purchase totals = $772.56       $833.9565   $833.96   $833.95   $833.90