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	$244.30	8.389%	$264.7943	$264.79	$264.80	$264.80
Purchase #2	$48.48	11.126%	$53.8739	$53.87	$53.85	$53.90
Purchase #3	$154.99	12.510%	$174.3792	$174.38	$174.40	$174.40
Purchase #4	$89.97	6.406%	$95.7335	$95.73	$95.75	$95.70
Purchase #5	$109.93	12.510%	$123.6822	$123.68	$123.70	$123.70
Purchase #6	$186.43	13.107%	$210.8654	$210.87	$210.85	$210.90
Purchase #7	$44.88	3.521%	$46.4602	$46.46	$46.45	$46.50
7 purchase totals =	$878.98		$969.7887	$969.78	$969.80	$969.90