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 $107.63   6.567%   $114.6981   $114.70   $114.70   $114.70  
  Purchase #2 $187.94   6.631%   $200.4023   $200.40   $200.40   $200.40  
  Purchase #3 $242.33   11.722%   $270.7359   $270.74   $270.75   $270.70  
  Purchase #4 $208.72   6.322%   $221.9153   $221.92   $221.90   $221.90  
  Purchase #5 $6.48   7.170%   $6.9446   $6.94   $6.95   $6.90  
  Purchase #6 $60.63   13.805%   $69   $69.00   $69.00   $69.00  
  Purchase #7 $212.73   10.785%   $235.6729   $235.67   $235.65   $235.70  
  7 purchase totals = $1,026.46       $1,119.3691   $1,119.37   $1,119.35   $1,119.30