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 $206.69   3.821%   $214.5876   $214.59   $214.60   $214.60  
  Purchase #2 $98.51   6.481%   $104.8944   $104.89   $104.90   $104.90  
  Purchase #3 $26.45   8.389%   $28.6689   $28.67   $28.65   $28.70  
  Purchase #4 $235.45   4.731%   $246.5891   $246.59   $246.60   $246.60  
  Purchase #5 $155.82   5.732%   $164.7516   $164.75   $164.75   $164.80  
  Purchase #6 $219.45   10.702%   $242.9355   $242.94   $242.95   $242.90  
  Purchase #7 $196.67   3.575%   $203.701   $203.70   $203.70   $203.70  
  7 purchase totals = $1,139.04       $1,206.1281   $1,206.13   $1,206.15   $1,206.20