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 $119.83   4.701%   $125.4632   $125.46   $125.45   $125.50  
  Purchase #2 $16.38   13.603%   $18.6082   $18.61   $18.60   $18.60  
  Purchase #3 $119.98   6.335%   $127.5807   $127.58   $127.60   $127.60  
  Purchase #4 $193.66   7.568%   $208.3162   $208.32   $208.30   $208.30  
  Purchase #5 $140.56   5.175%   $147.834   $147.83   $147.85   $147.80  
  Purchase #6 $191.43   6.672%   $204.2022   $204.20   $204.20   $204.20  
  Purchase #7 $87.45   10.342%   $96.4941   $96.49   $96.50   $96.50  
  7 purchase totals = $869.29       $928.4986   $928.49   $928.50   $928.50