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 $85.63   12.141%   $96.0263   $96.03   $96.05   $96.00  
  Purchase #2 $203.36   5.598%   $214.7441   $214.74   $214.75   $214.70  
  Purchase #3 $83.49   5.510%   $88.0903   $88.09   $88.10   $88.10  
  Purchase #4 $248.84   9.760%   $273.1268   $273.13   $273.15   $273.10  
  Purchase #5 $190.74   13.558%   $216.6005   $216.60   $216.60   $216.60  
  Purchase #6 $228.81   11.384%   $254.8577   $254.86   $254.85   $254.90  
  Purchase #7 $104.42   13.267%   $118.2734   $118.27   $118.25   $118.30  
  7 purchase totals = $1,145.29       $1,261.7191   $1,261.72   $1,261.75   $1,261.70