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 $119.51   3.327%   $123.4861   $123.49   $123.50   $123.50  
  Purchase #2 $91.85   5.394%   $96.8044   $96.80   $96.80   $96.80  
  Purchase #3 $151.70   3.275%   $156.6682   $156.67   $156.65   $156.70  
  Purchase #4 $14.54   3.536%   $15.0541   $15.05   $15.05   $15.10  
  Purchase #5 $222.80   9.177%   $243.2464   $243.25   $243.25   $243.20  
  Purchase #6 $207.71   7.239%   $222.7461   $222.75   $222.75   $222.70  
  Purchase #7 $162.54   3.476%   $168.1899   $168.19   $168.20   $168.20  
  7 purchase totals = $970.65       $1,026.1952   $1,026.20   $1,026.20   $1,026.20