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	$47.31	13.250%	$53.5786	$53.58	$53.60	$53.60
Purchase #2	$75.76	4.251%	$78.9806	$78.98	$79.00	$79.00
Purchase #3	$114.41	8.824%	$124.5055	$124.51	$124.50	$124.50
Purchase #4	$202.96	3.836%	$210.7455	$210.75	$210.75	$210.70
Purchase #5	$57.46	3.644%	$59.5538	$59.55	$59.55	$59.60
Purchase #6	$10.58	8.204%	$11.448	$11.45	$11.45	$11.40
Purchase #7	$106.42	4.690%	$111.4111	$111.41	$111.40	$111.40
7 purchase totals =	$614.90		$650.2231	$650.23	$650.25	$650.20