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 $119.33   5.584%   $125.9934   $125.99   $126.00   $126.00  
  Purchase #2 $225.48   6.371%   $239.8453   $239.85   $239.85   $239.80  
  Purchase #3 $187.98   9.551%   $205.934   $205.93   $205.95   $205.90  
  Purchase #4 $230.70   10.467%   $254.8474   $254.85   $254.85   $254.80  
  Purchase #5 $100.81   8.401%   $109.279   $109.28   $109.30   $109.30  
  Purchase #6 $130.63   13.485%   $148.2455   $148.25   $148.25   $148.20  
  Purchase #7 $244.52   8.812%   $266.0671   $266.07   $266.05   $266.10  
  7 purchase totals = $1,239.45       $1,350.2117   $1,350.22   $1,350.25   $1,350.10