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 $96.34   7.328%   $103.3998   $103.40   $103.40   $103.40  
  Purchase #2 $50.41   11.742%   $56.3291   $56.33   $56.35   $56.30  
  Purchase #3 $44.29   7.479%   $47.6024   $47.60   $47.60   $47.60  
  Purchase #4 $194.97   5.459%   $205.6134   $205.61   $205.60   $205.60  
  Purchase #5 $87.38   10.808%   $96.824   $96.82   $96.80   $96.80  
  Purchase #6 $10.77   6.537%   $11.474   $11.47   $11.45   $11.50  
  Purchase #7 $208.46   12.337%   $234.1777   $234.18   $234.20   $234.20  
  7 purchase totals = $692.62       $755.4204   $755.41   $755.40   $755.40