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 $109.99   3.653%   $114.0079   $114.01   $114.00   $114.00  
  Purchase #2 $14.91   5.679%   $15.7567   $15.76   $15.75   $15.80  
  Purchase #3 $106.43   6.128%   $112.952   $112.95   $112.95   $113.00  
  Purchase #4 $145.43   5.435%   $153.3341   $153.33   $153.35   $153.30  
  Purchase #5 $56.40   8.145%   $60.9938   $60.99   $61.00   $61.00  
  Purchase #6 $98.96   3.486%   $102.4097   $102.41   $102.40   $102.40  
  Purchase #7 $160.35   3.475%   $165.9222   $165.92   $165.90   $165.90  
  7 purchase totals = $692.47       $725.3764   $725.37   $725.35   $725.40