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	$66.41	9.259%	$72.5589	$72.56	$72.55	$72.60
Purchase #2	$205.61	11.527%	$229.3107	$229.31	$229.30	$229.30
Purchase #3	$130.32	4.385%	$136.0345	$136.03	$136.05	$136.00
Purchase #4	$126.95	5.616%	$134.0795	$134.08	$134.10	$134.10
Purchase #5	$96.89	11.749%	$108.2736	$108.27	$108.25	$108.30
Purchase #6	$249.33	11.698%	$278.4966	$278.50	$278.50	$278.50
Purchase #7	$223.82	6.226%	$237.755	$237.76	$237.75	$237.80
7 purchase totals =	$1,099.33		$1,196.5088	$1,196.51	$1,196.50	$1,196.60