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	$102.80	6.657%	$109.6434	$109.64	$109.65	$109.60
Purchase #2	$153.80	4.429%	$160.6118	$160.61	$160.60	$160.60
Purchase #3	$49.49	10.103%	$54.49	$54.49	$54.50	$54.50
Purchase #4	$189.94	10.795%	$210.444	$210.44	$210.45	$210.40
Purchase #5	$249.57	11.258%	$277.6666	$277.67	$277.65	$277.70
Purchase #6	$51.41	4.194%	$53.5661	$53.57	$53.55	$53.60
Purchase #7	$211.49	9.449%	$231.4737	$231.47	$231.45	$231.50
7 purchase totals =	$1,008.50		$1,097.8956	$1,097.89	$1,097.85	$1,097.90