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 $105.84   8.163%   $114.4797   $114.48   $114.50   $114.50  
  Purchase #2 $97.35   10.596%   $107.6652   $107.67   $107.65   $107.70  
  Purchase #3 $165.74   6.657%   $176.7733   $176.77   $176.75   $176.80  
  Purchase #4 $142.51   8.553%   $154.6989   $154.70   $154.70   $154.70  
  Purchase #5 $13.54   6.754%   $14.4545   $14.45   $14.45   $14.50  
  Purchase #6 $170.56   5.394%   $179.76   $179.76   $179.75   $179.80  
  Purchase #7 $241.26   12.356%   $271.0701   $271.07   $271.05   $271.10  
  7 purchase totals = $936.80       $1,018.9017   $1,018.90   $1,018.85   $1,019.10