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	$153.75	3.346%	$158.8945	$158.89	$158.90	$158.90
Purchase #2	$129.93	10.509%	$143.5843	$143.58	$143.60	$143.60
Purchase #3	$33.88	9.613%	$37.1369	$37.14	$37.15	$37.10
Purchase #4	$185.45	10.284%	$204.5217	$204.52	$204.50	$204.50
Purchase #5	$169.26	12.596%	$190.58	$190.58	$190.60	$190.60
Purchase #6	$166.55	9.164%	$181.8126	$181.81	$181.80	$181.80
Purchase #7	$91.31	5.721%	$96.5338	$96.53	$96.55	$96.50
7 purchase totals =	$930.13		$1,013.0638	$1,013.05	$1,013.10	$1,013.00