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	$170.79	8.486%	$185.2832	$185.28	$185.30	$185.30
Purchase #2	$140.39	8.526%	$152.3597	$152.36	$152.35	$152.40
Purchase #3	$177.62	3.808%	$184.3838	$184.38	$184.40	$184.40
Purchase #4	$13.35	5.841%	$14.1298	$14.13	$14.15	$14.10
Purchase #5	$147.60	3.395%	$152.611	$152.61	$152.60	$152.60
Purchase #6	$192.45	13.302%	$218.0497	$218.05	$218.05	$218.00
Purchase #7	$155.39	4.577%	$162.5022	$162.50	$162.50	$162.50
7 purchase totals =	$997.59		$1,069.3194	$1,069.31	$1,069.35	$1,069.30