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	$103.91	7.284%	$111.4788	$111.48	$111.50	$111.50
Purchase #2	$249.29	6.640%	$265.8429	$265.84	$265.85	$265.80
Purchase #3	$175.83	9.540%	$192.6042	$192.60	$192.60	$192.60
Purchase #4	$159.90	7.666%	$172.1579	$172.16	$172.15	$172.20
Purchase #5	$217.61	6.204%	$231.1105	$231.11	$231.10	$231.10
Purchase #6	$209.63	3.403%	$216.7637	$216.76	$216.75	$216.80
Purchase #7	$56.62	13.795%	$64.4307	$64.43	$64.45	$64.40
7 purchase totals =	$1,172.79		$1,254.3887	$1,254.38	$1,254.40	$1,254.40