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	$142.46	11.448%	$158.7688	$158.77	$158.75	$158.80
Purchase #2	$153.52	7.498%	$165.0309	$165.03	$165.05	$165.00
Purchase #3	$243.82	4.621%	$255.0869	$255.09	$255.10	$255.10
Purchase #4	$22.48	12.472%	$25.2837	$25.28	$25.30	$25.30
Purchase #5	$115.61	4.163%	$120.4228	$120.42	$120.40	$120.40
Purchase #6	$175.88	11.655%	$196.3788	$196.38	$196.40	$196.40
Purchase #7	$82.91	5.504%	$87.4734	$87.47	$87.45	$87.50
7 purchase totals =	$936.68		$1,008.4453	$1,008.44	$1,008.45	$1,008.50