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 $187.93   8.143%   $203.2331   $203.23   $203.25   $203.20  
  Purchase #2 $223.97   8.135%   $242.19   $242.19   $242.20   $242.20  
  Purchase #3 $243.85   5.692%   $257.7299   $257.73   $257.75   $257.70  
  Purchase #4 $93.42   6.420%   $99.4176   $99.42   $99.40   $99.40  
  Purchase #5 $214.34   5.353%   $225.8136   $225.81   $225.80   $225.80  
  Purchase #6 $245.66   7.247%   $263.463   $263.46   $263.45   $263.50  
  Purchase #7 $107.34   6.382%   $114.1904   $114.19   $114.20   $114.20  
  7 purchase totals = $1,316.51       $1,406.0376   $1,406.03   $1,406.05   $1,406.00