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 $178.48   9.770%   $195.9175   $195.92   $195.90   $195.90  
  Purchase #2 $88.91   9.865%   $97.681   $97.68   $97.70   $97.70  
  Purchase #3 $68.93   8.413%   $74.7291   $74.73   $74.75   $74.70  
  Purchase #4 $60.72   9.111%   $66.2522   $66.25   $66.25   $66.30  
  Purchase #5 $62.40   10.310%   $68.8334   $68.83   $68.85   $68.80  
  Purchase #6 $174.95   10.411%   $193.164   $193.16   $193.15   $193.20  
  Purchase #7 $63.69   3.406%   $65.8593   $65.86   $65.85   $65.90  
  7 purchase totals = $698.08       $762.4365   $762.43   $762.45   $762.50