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	$141.41	8.488%	$153.4129	$153.41	$153.40	$153.40
Purchase #2	$79.38	11.255%	$88.3142	$88.31	$88.30	$88.30
Purchase #3	$54.79	9.477%	$59.9824	$59.98	$60.00	$60.00
Purchase #4	$133.66	11.436%	$148.9454	$148.95	$148.95	$148.90
Purchase #5	$229.48	6.585%	$244.5913	$244.59	$244.60	$244.60
Purchase #6	$59.56	5.388%	$62.7691	$62.77	$62.75	$62.80
Purchase #7	$78.42	13.261%	$88.8193	$88.82	$88.80	$88.80
7 purchase totals =	$776.70		$846.8346	$846.83	$846.80	$846.80