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 $196.97   3.161%   $203.1962   $203.20   $203.20   $203.20  
  Purchase #2 $202.29   4.181%   $210.7477   $210.75   $210.75   $210.70  
  Purchase #3 $175.36   10.838%   $194.3655   $194.37   $194.35   $194.40  
  Purchase #4 $60.34   7.183%   $64.6742   $64.67   $64.65   $64.70  
  Purchase #5 $166.62   5.231%   $175.3359   $175.34   $175.35   $175.30  
  Purchase #6 $233.54   5.606%   $246.6323   $246.63   $246.65   $246.60  
  Purchase #7 $172.51   11.401%   $192.1779   $192.18   $192.20   $192.20  
  7 purchase totals = $1,207.63       $1,287.1297   $1,287.14   $1,287.15   $1,287.10