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 $232.98   12.708%   $262.5871   $262.59   $262.60   $262.60  
  Purchase #2 $213.52   13.327%   $241.9758   $241.98   $242.00   $242.00  
  Purchase #3 $248.86   9.350%   $272.1284   $272.13   $272.15   $272.10  
  Purchase #4 $134.93   9.159%   $147.2882   $147.29   $147.30   $147.30  
  Purchase #5 $69.85   11.277%   $77.727   $77.73   $77.75   $77.70  
  Purchase #6 $46.44   12.528%   $52.258   $52.26   $52.25   $52.30  
  Purchase #7 $106.97   7.440%   $114.9286   $114.93   $114.95   $114.90  
  7 purchase totals = $1,053.55       $1,168.8931   $1,168.91   $1,169.00   $1,168.90