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	$204.83	11.436%	$228.2544	$228.25	$228.25	$228.30
Purchase #2	$57.56	3.826%	$59.7622	$59.76	$59.75	$59.80
Purchase #3	$225.89	9.589%	$247.5506	$247.55	$247.55	$247.60
Purchase #4	$136.74	5.634%	$144.4439	$144.44	$144.45	$144.40
Purchase #5	$49.56	13.618%	$56.3091	$56.31	$56.30	$56.30
Purchase #6	$71.76	5.362%	$75.6078	$75.61	$75.60	$75.60
Purchase #7	$163.63	5.405%	$172.4742	$172.47	$172.45	$172.50
7 purchase totals =	$909.97		$984.4022	$984.39	$984.35	$984.50