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	$99.69	11.742%	$111.3956	$111.40	$111.40	$111.40
Purchase #2	$85.77	10.128%	$94.4568	$94.46	$94.45	$94.50
Purchase #3	$101.89	10.486%	$112.5742	$112.57	$112.55	$112.60
Purchase #4	$127.94	6.418%	$136.1512	$136.15	$136.15	$136.20
Purchase #5	$158.79	7.766%	$171.1216	$171.12	$171.10	$171.10
Purchase #6	$219.64	7.335%	$235.7506	$235.75	$235.75	$235.80
Purchase #7	$169.47	8.141%	$183.2666	$183.27	$183.25	$183.30
7 purchase totals =	$963.19		$1,044.7166	$1,044.72	$1,044.65	$1,044.90