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 $204.45   9.674%   $224.2285   $224.23   $224.25   $224.20  
  Purchase #2 $164.38   12.213%   $184.4557   $184.46   $184.45   $184.50  
  Purchase #3 $30.34   7.873%   $32.7287   $32.73   $32.75   $32.70  
  Purchase #4 $167.29   10.189%   $184.3352   $184.34   $184.35   $184.30  
  Purchase #5 $129.66   4.329%   $135.273   $135.27   $135.25   $135.30  
  Purchase #6 $59.64   3.871%   $61.9487   $61.95   $61.95   $61.90  
  Purchase #7 $229.38   7.301%   $246.127   $246.13   $246.15   $246.10  
  7 purchase totals = $985.14       $1,069.0968   $1,069.11   $1,069.15   $1,069.00