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 $214.89   8.802%   $233.8046   $233.80   $233.80   $233.80  
  Purchase #2 $218.60   9.561%   $239.5003   $239.50   $239.50   $239.50  
  Purchase #3 $60.51   7.825%   $65.2449   $65.24   $65.25   $65.20  
  Purchase #4 $200.28   4.274%   $208.84   $208.84   $208.85   $208.80  
  Purchase #5 $85.57   10.233%   $94.3264   $94.33   $94.35   $94.30  
  Purchase #6 $72.58   8.811%   $78.975   $78.98   $79.00   $79.00  
  Purchase #7 $89.69   3.457%   $92.7906   $92.79   $92.80   $92.80  
  7 purchase totals = $942.12       $1,013.4818   $1,013.48   $1,013.55   $1,013.40