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 $231.75   5.566%   $244.6492   $244.65   $244.65   $244.60  
  Purchase #2 $193.78   10.296%   $213.7316   $213.73   $213.75   $213.70  
  Purchase #3 $191.98   4.612%   $200.8341   $200.83   $200.85   $200.80  
  Purchase #4 $65.83   8.714%   $71.5664   $71.57   $71.55   $71.60  
  Purchase #5 $84.42   13.491%   $95.8091   $95.81   $95.80   $95.80  
  Purchase #6 $134.49   13.576%   $152.7484   $152.75   $152.75   $152.70  
  Purchase #7 $42.74   9.174%   $46.661   $46.66   $46.65   $46.70  
  7 purchase totals = $944.99       $1,025.9998   $1,026.00   $1,026.00   $1,025.90