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 $104.73   8.813%   $113.9599   $113.96   $113.95   $114.00  
  Purchase #2 $234.44   10.196%   $258.3435   $258.34   $258.35   $258.30  
  Purchase #3 $75.63   13.759%   $86.0359   $86.04   $86.05   $86.00  
  Purchase #4 $240.47   12.241%   $269.9059   $269.91   $269.90   $269.90  
  Purchase #5 $149.94   9.407%   $164.0449   $164.04   $164.05   $164.00  
  Purchase #6 $105.37   13.212%   $119.2915   $119.29   $119.30   $119.30  
  Purchase #7 $218.78   6.498%   $232.9963   $233.00   $233.00   $233.00  
  7 purchase totals = $1,129.36       $1,244.5779   $1,244.58   $1,244.60   $1,244.50