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 $97.57   8.680%   $106.0391   $106.04   $106.05   $106.00  
  Purchase #2 $164.41   10.702%   $182.0052   $182.01   $182.00   $182.00  
  Purchase #3 $56.73   8.762%   $61.7007   $61.70   $61.70   $61.70  
  Purchase #4 $193.43   3.774%   $200.73   $200.73   $200.75   $200.70  
  Purchase #5 $158.48   6.829%   $169.3026   $169.30   $169.30   $169.30  
  Purchase #6 $122.85   3.394%   $127.0195   $127.02   $127.00   $127.00  
  Purchase #7 $215.42   3.520%   $223.0028   $223.00   $223.00   $223.00  
  7 purchase totals = $1,008.89       $1,069.7999   $1,069.80   $1,069.80   $1,069.70