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	$215.73	8.150%	$233.312	$233.31	$233.30	$233.30
Purchase #2	$129.99	10.565%	$143.7234	$143.72	$143.70	$143.70
Purchase #3	$101.77	5.325%	$107.1893	$107.19	$107.20	$107.20
Purchase #4	$47.78	12.154%	$53.5872	$53.59	$53.60	$53.60
Purchase #5	$160.42	3.624%	$166.2336	$166.23	$166.25	$166.20
Purchase #6	$85.38	4.797%	$89.4757	$89.48	$89.50	$89.50
Purchase #7	$133.69	7.240%	$143.3692	$143.37	$143.35	$143.40
7 purchase totals =	$874.76		$936.8904	$936.89	$936.90	$936.90