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 $205.82   13.509%   $233.6242   $233.62   $233.60   $233.60  
  Purchase #2 $212.90   3.402%   $220.1429   $220.14   $220.15   $220.10  
  Purchase #3 $225.62   12.705%   $254.285   $254.29   $254.30   $254.30  
  Purchase #4 $189.31   10.232%   $208.6802   $208.68   $208.70   $208.70  
  Purchase #5 $32.57   7.357%   $34.9662   $34.97   $34.95   $35.00  
  Purchase #6 $40.88   11.561%   $45.6061   $45.61   $45.60   $45.60  
  Purchase #7 $127.73   7.236%   $136.9725   $136.97   $136.95   $137.00  
  7 purchase totals = $1,034.83       $1,134.2771   $1,134.28   $1,134.25   $1,134.30