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 $243.30   7.769%   $262.202   $262.20   $262.20   $262.20  
  Purchase #2 $53.65   5.234%   $56.458   $56.46   $56.45   $56.50  
  Purchase #3 $139.90   3.398%   $144.6538   $144.65   $144.65   $144.70  
  Purchase #4 $228.75   7.310%   $245.4716   $245.47   $245.45   $245.50  
  Purchase #5 $242.86   8.528%   $263.5711   $263.57   $263.55   $263.60  
  Purchase #6 $29.35   4.868%   $30.7788   $30.78   $30.80   $30.80  
  Purchase #7 $193.67   6.472%   $206.2043   $206.20   $206.20   $206.20  
  7 purchase totals = $1,131.48       $1,209.3396   $1,209.33   $1,209.30   $1,209.50