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 $41.89   4.204%   $43.6511   $43.65   $43.65   $43.70  
  Purchase #2 $50.59   6.569%   $53.9133   $53.91   $53.90   $53.90  
  Purchase #3 $115.26   9.135%   $125.789   $125.79   $125.80   $125.80  
  Purchase #4 $86.64   10.492%   $95.7303   $95.73   $95.75   $95.70  
  Purchase #5 $24.74   4.264%   $25.7949   $25.79   $25.80   $25.80  
  Purchase #6 $114.62   3.755%   $118.924   $118.92   $118.90   $118.90  
  Purchase #7 $216.83   7.873%   $233.901   $233.90   $233.90   $233.90  
  7 purchase totals = $650.57       $697.7036   $697.69   $697.70   $697.70