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 $172.76   13.857%   $196.6994   $196.70   $196.70   $196.70  
  Purchase #2 $223.93   13.435%   $254.015   $254.02   $254.00   $254.00  
  Purchase #3 $154.77   13.274%   $175.3142   $175.31   $175.30   $175.30  
  Purchase #4 $225.73   3.496%   $233.6215   $233.62   $233.60   $233.60  
  Purchase #5 $243.96   7.502%   $262.2619   $262.26   $262.25   $262.30  
  Purchase #6 $206.44   10.217%   $227.532   $227.53   $227.55   $227.50  
  Purchase #7 $78.71   5.366%   $82.9336   $82.93   $82.95   $82.90  
  7 purchase totals = $1,306.30       $1,432.3776   $1,432.37   $1,432.35   $1,432.30