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 $184.74   8.416%   $200.2877   $200.29   $200.30   $200.30  
  Purchase #2 $216.29   4.517%   $226.0598   $226.06   $226.05   $226.10  
  Purchase #3 $188.80   5.797%   $199.7447   $199.74   $199.75   $199.70  
  Purchase #4 $207.80   8.565%   $225.5981   $225.60   $225.60   $225.60  
  Purchase #5 $34.58   7.665%   $37.2306   $37.23   $37.25   $37.20  
  Purchase #6 $214.32   5.855%   $226.8684   $226.87   $226.85   $226.90  
  Purchase #7 $230.62   6.404%   $245.3889   $245.39   $245.40   $245.40  
  7 purchase totals = $1,277.15       $1,361.1782   $1,361.18   $1,361.20   $1,361.20