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 $188.85   4.184%   $196.7515   $196.75   $196.75   $196.80  
  Purchase #2 $97.90   3.271%   $101.1023   $101.10   $101.10   $101.10  
  Purchase #3 $94.84   13.132%   $107.2944   $107.29   $107.30   $107.30  
  Purchase #4 $197.55   10.165%   $217.631   $217.63   $217.65   $217.60  
  Purchase #5 $161.74   7.699%   $174.1924   $174.19   $174.20   $174.20  
  Purchase #6 $105.32   13.417%   $119.4508   $119.45   $119.45   $119.50  
  Purchase #7 $102.73   4.249%   $107.095   $107.10   $107.10   $107.10  
  7 purchase totals = $948.93       $1,023.5174   $1,023.51   $1,023.55   $1,023.60