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	$152.61	13.345%	$172.9758	$172.98	$173.00	$173.00
Purchase #2	$179.51	4.656%	$187.868	$187.87	$187.85	$187.90
Purchase #3	$172.87	4.310%	$180.3207	$180.32	$180.30	$180.30
Purchase #4	$26.42	6.674%	$28.1833	$28.18	$28.20	$28.20
Purchase #5	$185.87	13.351%	$210.6855	$210.69	$210.70	$210.70
Purchase #6	$153.64	10.406%	$169.6278	$169.63	$169.65	$169.60
Purchase #7	$101.81	9.759%	$111.7456	$111.75	$111.75	$111.70
7 purchase totals =	$972.73		$1,061.4067	$1,061.42	$1,061.45	$1,061.40