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 $193.85   4.151%   $201.8967   $201.90   $201.90   $201.90  
  Purchase #2 $188.36   3.674%   $195.2803   $195.28   $195.30   $195.30  
  Purchase #3 $214.38   8.498%   $232.598   $232.60   $232.60   $232.60  
  Purchase #4 $166.30   11.614%   $185.6141   $185.61   $185.60   $185.60  
  Purchase #5 $60.83   4.337%   $63.4682   $63.47   $63.45   $63.50  
  Purchase #6 $206.35   7.349%   $221.5147   $221.51   $221.50   $221.50  
  Purchase #7 $87.95   8.630%   $95.5401   $95.54   $95.55   $95.50  
  7 purchase totals = $1,118.02       $1,195.9121   $1,195.91   $1,195.90   $1,195.90