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 $210.64   11.574%   $235.0195   $235.02   $235.00   $235.00  
  Purchase #2 $60.56   13.211%   $68.5606   $68.56   $68.55   $68.60  
  Purchase #3 $51.42   3.136%   $53.0325   $53.03   $53.05   $53.00  
  Purchase #4 $203.66   8.786%   $221.5536   $221.55   $221.55   $221.60  
  Purchase #5 $249.83   8.503%   $271.073   $271.07   $271.05   $271.10  
  Purchase #6 $70.48   7.820%   $75.9915   $75.99   $76.00   $76.00  
  Purchase #7 $188.92   11.645%   $210.9197   $210.92   $210.90   $210.90  
  7 purchase totals = $1,035.51       $1,136.1504   $1,136.14   $1,136.10   $1,136.20