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 $88.55   7.574%   $95.2568   $95.26   $95.25   $95.30  
  Purchase #2 $114.67   3.743%   $118.9621   $118.96   $118.95   $119.00  
  Purchase #3 $78.77   6.518%   $83.9042   $83.90   $83.90   $83.90  
  Purchase #4 $14.91   3.608%   $15.448   $15.45   $15.45   $15.40  
  Purchase #5 $233.42   6.448%   $248.4709   $248.47   $248.45   $248.50  
  Purchase #6 $111.55   12.257%   $125.2227   $125.22   $125.20   $125.20  
  Purchase #7 $41.41   5.536%   $43.7025   $43.70   $43.70   $43.70  
  7 purchase totals = $683.28       $730.9672   $730.96   $730.90   $731.00