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 $114.81   4.117%   $119.5367   $119.54   $119.55   $119.50  
  Purchase #2 $155.44   9.188%   $169.7218   $169.72   $169.70   $169.70  
  Purchase #3 $118.28   7.311%   $126.9275   $126.93   $126.95   $126.90  
  Purchase #4 $174.35   4.597%   $182.3649   $182.36   $182.35   $182.40  
  Purchase #5 $109.85   3.608%   $113.8134   $113.81   $113.80   $113.80  
  Purchase #6 $186.28   13.368%   $211.1819   $211.18   $211.20   $211.20  
  Purchase #7 $115.45   8.762%   $125.5657   $125.57   $125.55   $125.60  
  7 purchase totals = $974.46       $1,049.1119   $1,049.11   $1,049.10   $1,049.10