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 $201.34   6.266%   $213.956   $213.96   $213.95   $214.00  
  Purchase #2 $99.85   12.355%   $112.1865   $112.19   $112.20   $112.20  
  Purchase #3 $224.80   10.254%   $247.851   $247.85   $247.85   $247.90  
  Purchase #4 $207.35   7.405%   $222.7043   $222.70   $222.70   $222.70  
  Purchase #5 $199.72   4.603%   $208.9131   $208.91   $208.90   $208.90  
  Purchase #6 $203.34   5.328%   $214.174   $214.17   $214.15   $214.20  
  Purchase #7 $184.82   6.491%   $196.8167   $196.82   $196.80   $196.80  
  7 purchase totals = $1,321.22       $1,416.6016   $1,416.60   $1,416.55   $1,416.70