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 $54.80   13.801%   $62.3629   $62.36   $62.35   $62.40  
  Purchase #2 $116.81   7.246%   $125.2741   $125.27   $125.25   $125.30  
  Purchase #3 $242.66   13.240%   $274.7882   $274.79   $274.80   $274.80  
  Purchase #4 $185.39   6.154%   $196.7989   $196.80   $196.80   $196.80  
  Purchase #5 $30.66   5.400%   $32.3156   $32.32   $32.30   $32.30  
  Purchase #6 $213.90   6.394%   $227.5768   $227.58   $227.60   $227.60  
  Purchase #7 $240.66   5.109%   $252.9553   $252.96   $252.95   $253.00  
  7 purchase totals = $1,084.88       $1,172.0718   $1,172.08   $1,172.05   $1,172.20