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 $41.26   11.806%   $46.1312   $46.13   $46.15   $46.10  
  Purchase #2 $179.39   7.291%   $192.4693   $192.47   $192.45   $192.50  
  Purchase #3 $188.82   4.208%   $196.7655   $196.77   $196.75   $196.80  
  Purchase #4 $147.60   6.834%   $157.687   $157.69   $157.70   $157.70  
  Purchase #5 $168.95   5.653%   $178.5007   $178.50   $178.50   $178.50  
  Purchase #6 $248.25   4.648%   $259.7887   $259.79   $259.80   $259.80  
  Purchase #7 $131.41   10.641%   $145.3933   $145.39   $145.40   $145.40  
  7 purchase totals = $1,105.68       $1,176.7357   $1,176.74   $1,176.75   $1,176.80