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 $161.69   3.260%   $166.9611   $166.96   $166.95   $167.00  
  Purchase #2 $217.60   11.467%   $242.5522   $242.55   $242.55   $242.60  
  Purchase #3 $192.68   6.632%   $205.4585   $205.46   $205.45   $205.50  
  Purchase #4 $199.78   6.188%   $212.1424   $212.14   $212.15   $212.10  
  Purchase #5 $190.47   12.271%   $213.8426   $213.84   $213.85   $213.80  
  Purchase #6 $27.32   6.585%   $29.119   $29.12   $29.10   $29.10  
  Purchase #7 $172.69   11.713%   $192.9172   $192.92   $192.90   $192.90  
  7 purchase totals = $1,162.23       $1,262.9930   $1,262.99   $1,262.95   $1,263.00