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 $88.77   7.246%   $95.2023   $95.20   $95.20   $95.20  
  Purchase #2 $151.26   6.449%   $161.0148   $161.01   $161.00   $161.00  
  Purchase #3 $73.46   3.589%   $76.0965   $76.10   $76.10   $76.10  
  Purchase #4 $218.25   13.778%   $248.3205   $248.32   $248.30   $248.30  
  Purchase #5 $115.25   3.799%   $119.6283   $119.63   $119.65   $119.60  
  Purchase #6 $49.85   6.258%   $52.9696   $52.97   $52.95   $53.00  
  Purchase #7 $226.32   7.211%   $242.6399   $242.64   $242.65   $242.60  
  7 purchase totals = $923.16       $995.8719   $995.87   $995.85   $995.80