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 $215.60   10.701%   $238.6714   $238.67   $238.65   $238.70  
  Purchase #2 $249.68   13.348%   $283.0073   $283.01   $283.00   $283.00  
  Purchase #3 $211.49   10.192%   $233.0451   $233.05   $233.05   $233.00  
  Purchase #4 $208.36   5.339%   $219.4843   $219.48   $219.50   $219.50  
  Purchase #5 $118.90   12.283%   $133.5045   $133.50   $133.50   $133.50  
  Purchase #6 $248.64   3.587%   $257.5587   $257.56   $257.55   $257.60  
  Purchase #7 $94.87   3.321%   $98.0206   $98.02   $98.00   $98.00  
  7 purchase totals = $1,347.54       $1,463.2919   $1,463.29   $1,463.25   $1,463.30