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 $168.84   3.374%   $174.5367   $174.54   $174.55   $174.50  
  Purchase #2 $109.38   9.667%   $119.9538   $119.95   $119.95   $120.00  
  Purchase #3 $53.64   4.632%   $56.1246   $56.12   $56.10   $56.10  
  Purchase #4 $136.94   5.743%   $144.8045   $144.80   $144.80   $144.80  
  Purchase #5 $145.51   8.162%   $157.3865   $157.39   $157.40   $157.40  
  Purchase #6 $93.91   12.501%   $105.6497   $105.65   $105.65   $105.60  
  Purchase #7 $8.97   3.476%   $9.2818   $9.28   $9.30   $9.30  
  7 purchase totals = $717.19       $767.7376   $767.73   $767.75   $767.70