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	$245.37	6.257%	$260.7228	$260.72	$260.70	$260.70
Purchase #2	$244.38	3.322%	$252.4983	$252.50	$252.50	$252.50
Purchase #3	$164.61	6.103%	$174.6561	$174.66	$174.65	$174.70
Purchase #4	$80.40	3.404%	$83.1368	$83.14	$83.15	$83.10
Purchase #5	$93.50	8.581%	$101.5232	$101.52	$101.50	$101.50
Purchase #6	$188.32	9.707%	$206.6002	$206.60	$206.60	$206.60
Purchase #7	$81.69	10.631%	$90.3745	$90.37	$90.35	$90.40
7 purchase totals =	$1,098.27		$1,169.5119	$1,169.51	$1,169.45	$1,169.50