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	$62.31	7.320%	$66.8711	$66.87	$66.85	$66.90
Purchase #2	$172.43	7.232%	$184.9001	$184.90	$184.90	$184.90
Purchase #3	$244.59	5.195%	$257.2965	$257.30	$257.30	$257.30
Purchase #4	$55.88	12.116%	$62.6504	$62.65	$62.65	$62.70
Purchase #5	$127.40	6.856%	$136.1345	$136.13	$136.15	$136.10
Purchase #6	$34.78	7.717%	$37.464	$37.46	$37.45	$37.50
Purchase #7	$30.77	10.255%	$33.9255	$33.93	$33.95	$33.90
7 purchase totals =	$728.16		$779.2421	$779.24	$779.25	$779.30