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 $107.57   6.230%   $114.2716   $114.27   $114.25   $114.30  
  Purchase #2 $167.52   5.505%   $176.742   $176.74   $176.75   $176.70  
  Purchase #3 $57.85   7.777%   $62.349   $62.35   $62.35   $62.30  
  Purchase #4 $197.70   6.476%   $210.5031   $210.50   $210.50   $210.50  
  Purchase #5 $240.92   4.821%   $252.5348   $252.53   $252.55   $252.50  
  Purchase #6 $69.98   13.246%   $79.2496   $79.25   $79.25   $79.20  
  Purchase #7 $118.27   4.413%   $123.4893   $123.49   $123.50   $123.50  
  7 purchase totals = $959.81       $1,019.1394   $1,019.13   $1,019.15   $1,019.00