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	$165.33	13.634%	$187.8711	$187.87	$187.85	$187.90
Purchase #2	$154.60	11.127%	$171.8023	$171.80	$171.80	$171.80
Purchase #3	$204.83	10.103%	$225.524	$225.52	$225.50	$225.50
Purchase #4	$152.82	8.244%	$165.4185	$165.42	$165.40	$165.40
Purchase #5	$186.56	3.853%	$193.7482	$193.75	$193.75	$193.70
Purchase #6	$69.78	12.452%	$78.469	$78.47	$78.45	$78.50
Purchase #7	$188.25	3.526%	$194.8877	$194.89	$194.90	$194.90
7 purchase totals =	$1,122.17		$1,217.7208	$1,217.72	$1,217.65	$1,217.70