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 $214.69   7.577%   $230.9571   $230.96   $230.95   $231.00  
  Purchase #2 $212.48   9.677%   $233.0417   $233.04   $233.05   $233.00  
  Purchase #3 $210.30   8.270%   $227.6918   $227.69   $227.70   $227.70  
  Purchase #4 $30.83   8.358%   $33.4068   $33.41   $33.40   $33.40  
  Purchase #5 $196.93   8.265%   $213.2063   $213.21   $213.20   $213.20  
  Purchase #6 $209.39   8.528%   $227.2468   $227.25   $227.25   $227.20  
  Purchase #7 $223.98   10.368%   $247.2022   $247.20   $247.20   $247.20  
  7 purchase totals = $1,298.60       $1,412.7527   $1,412.76   $1,412.75   $1,412.70