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 $91.88   4.264%   $95.7978   $95.80   $95.80   $95.80  
  Purchase #2 $122.50   8.247%   $132.6026   $132.60   $132.60   $132.60  
  Purchase #3 $173.63   5.824%   $183.7422   $183.74   $183.75   $183.70  
  Purchase #4 $239.92   6.440%   $255.3708   $255.37   $255.35   $255.40  
  Purchase #5 $168.86   9.692%   $185.2259   $185.23   $185.25   $185.20  
  Purchase #6 $200.94   6.523%   $214.0473   $214.05   $214.05   $214.00  
  Purchase #7 $31.29   10.572%   $34.598   $34.60   $34.60   $34.60  
  7 purchase totals = $1,029.02       $1,101.3846   $1,101.39   $1,101.40   $1,101.30