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	$54.91	4.565%	$57.4166	$57.42	$57.40	$57.40
Purchase #2	$243.84	4.399%	$254.5665	$254.57	$254.55	$254.60
Purchase #3	$230.39	4.230%	$240.1355	$240.14	$240.15	$240.10
Purchase #4	$148.30	11.611%	$165.5191	$165.52	$165.50	$165.50
Purchase #5	$160.72	9.399%	$175.8261	$175.83	$175.85	$175.80
Purchase #6	$68.62	5.763%	$72.5746	$72.57	$72.55	$72.60
Purchase #7	$92.51	7.838%	$99.7609	$99.76	$99.75	$99.80
7 purchase totals =	$999.29		$1,065.7993	$1,065.81	$1,065.75	$1,065.80