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	$142.29	11.228%	$158.2663	$158.27	$158.25	$158.30
Purchase #2	$152.50	5.640%	$161.101	$161.10	$161.10	$161.10
Purchase #3	$242.43	10.117%	$266.9566	$266.96	$266.95	$267.00
Purchase #4	$210.42	6.183%	$223.4303	$223.43	$223.45	$223.40
Purchase #5	$231.38	10.343%	$255.3116	$255.31	$255.30	$255.30
Purchase #6	$161.87	11.139%	$179.9007	$179.90	$179.90	$179.90
Purchase #7	$14.58	5.252%	$15.3457	$15.35	$15.35	$15.30
7 purchase totals =	$1,155.47		$1,260.3122	$1,260.32	$1,260.30	$1,260.30