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	$102.87	8.809%	$111.9318	$111.93	$111.95	$111.90
Purchase #2	$172.40	10.821%	$191.0554	$191.06	$191.05	$191.10
Purchase #3	$148.50	7.162%	$159.1356	$159.14	$159.15	$159.10
Purchase #4	$72.55	11.261%	$80.7199	$80.72	$80.70	$80.70
Purchase #5	$240.36	5.561%	$253.7264	$253.73	$253.75	$253.70
Purchase #6	$139.47	13.753%	$158.6513	$158.65	$158.65	$158.70
Purchase #7	$222.46	4.106%	$231.5942	$231.59	$231.60	$231.60
7 purchase totals =	$1,098.61		$1,186.8146	$1,186.82	$1,186.85	$1,186.80