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 $101.99   11.810%   $114.035   $114.04   $114.05   $114.00  
  Purchase #2 $249.66   12.287%   $280.3357   $280.34   $280.35   $280.30  
  Purchase #3 $142.84   6.647%   $152.3346   $152.33   $152.35   $152.30  
  Purchase #4 $163.68   8.716%   $177.9463   $177.95   $177.95   $177.90  
  Purchase #5 $228.75   5.673%   $241.727   $241.73   $241.75   $241.70  
  Purchase #6 $165.80   4.568%   $173.3737   $173.37   $173.35   $173.40  
  Purchase #7 $158.28   11.819%   $176.9871   $176.99   $177.00   $177.00  
  7 purchase totals = $1,211.00       $1,316.7394   $1,316.75   $1,316.80   $1,316.60