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 $24.69   5.802%   $26.1225   $26.12   $26.10   $26.10  
  Purchase #2 $192.29   11.442%   $214.2918   $214.29   $214.30   $214.30  
  Purchase #3 $80.94   9.667%   $88.7645   $88.76   $88.75   $88.80  
  Purchase #4 $236.48   6.831%   $252.6339   $252.63   $252.65   $252.60  
  Purchase #5 $69.47   6.464%   $73.9605   $73.96   $73.95   $74.00  
  Purchase #6 $239.57   8.659%   $260.3144   $260.31   $260.30   $260.30  
  Purchase #7 $84.97   11.674%   $94.8894   $94.89   $94.90   $94.90  
  7 purchase totals = $928.41       $1,010.9770   $1,010.96   $1,010.95   $1,011.00