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	$88.96	13.145%	$100.6538	$100.65	$100.65	$100.70
Purchase #2	$104.28	5.139%	$109.6389	$109.64	$109.65	$109.60
Purchase #3	$17.50	7.774%	$18.8605	$18.86	$18.85	$18.90
Purchase #4	$105.51	12.373%	$118.5648	$118.56	$118.55	$118.60
Purchase #5	$18.32	7.747%	$19.7393	$19.74	$19.75	$19.70
Purchase #6	$76.29	10.309%	$84.1547	$84.15	$84.15	$84.20
Purchase #7	$158.94	8.435%	$172.3466	$172.35	$172.35	$172.30
7 purchase totals =	$569.80		$623.9586	$623.95	$623.95	$624.00