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	$129.47	10.150%	$142.6112	$142.61	$142.60	$142.60
Purchase #2	$100.87	10.578%	$111.54	$111.54	$111.55	$111.50
Purchase #3	$94.27	13.698%	$107.1831	$107.18	$107.20	$107.20
Purchase #4	$89.59	6.152%	$95.1016	$95.10	$95.10	$95.10
Purchase #5	$83.75	9.770%	$91.9324	$91.93	$91.95	$91.90
Purchase #6	$129.66	13.849%	$147.6166	$147.62	$147.60	$147.60
Purchase #7	$100.30	4.842%	$105.1565	$105.16	$105.15	$105.20
7 purchase totals =	$727.91		$801.1414	$801.14	$801.15	$801.10