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 $231.71   4.292%   $241.655   $241.66   $241.65   $241.70  
  Purchase #2 $207.32   8.291%   $224.5089   $224.51   $224.50   $224.50  
  Purchase #3 $127.83   12.373%   $143.6464   $143.65   $143.65   $143.60  
  Purchase #4 $141.34   5.246%   $148.7547   $148.75   $148.75   $148.80  
  Purchase #5 $213.98   4.362%   $223.3138   $223.31   $223.30   $223.30  
  Purchase #6 $58.51   5.743%   $61.8702   $61.87   $61.85   $61.90  
  Purchase #7 $150.30   5.562%   $158.6597   $158.66   $158.65   $158.70  
  7 purchase totals = $1,130.99       $1,202.4087   $1,202.41   $1,202.35   $1,202.50