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 $76.73   11.553%   $85.5946   $85.59   $85.60   $85.60  
  Purchase #2 $208.47   3.492%   $215.7498   $215.75   $215.75   $215.70  
  Purchase #3 $98.36   12.857%   $111.0061   $111.01   $111.00   $111.00  
  Purchase #4 $212.54   4.681%   $222.489   $222.49   $222.50   $222.50  
  Purchase #5 $242.37   4.569%   $253.4439   $253.44   $253.45   $253.40  
  Purchase #6 $161.66   3.373%   $167.1128   $167.11   $167.10   $167.10  
  Purchase #7 $129.57   9.384%   $141.7288   $141.73   $141.75   $141.70  
  7 purchase totals = $1,129.70       $1,197.1250   $1,197.12   $1,197.15   $1,197.00