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 $76.30   11.211%   $84.854   $84.85   $84.85   $84.90  
  Purchase #2 $98.60   8.322%   $106.8055   $106.81   $106.80   $106.80  
  Purchase #3 $32.44   3.590%   $33.6046   $33.60   $33.60   $33.60  
  Purchase #4 $141.33   4.800%   $148.1138   $148.11   $148.10   $148.10  
  Purchase #5 $101.29   8.713%   $110.1154   $110.12   $110.10   $110.10  
  Purchase #6 $193.28   11.712%   $215.917   $215.92   $215.90   $215.90  
  Purchase #7 $241.51   4.631%   $252.6943   $252.69   $252.70   $252.70  
  7 purchase totals = $884.75       $952.1046   $952.10   $952.05   $952.10