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	$145.54	10.237%	$160.4389	$160.44	$160.45	$160.40
Purchase #2	$19.82	6.611%	$21.1303	$21.13	$21.15	$21.10
Purchase #3	$191.69	5.538%	$202.3058	$202.31	$202.30	$202.30
Purchase #4	$231.47	12.218%	$259.751	$259.75	$259.75	$259.80
Purchase #5	$165.66	9.635%	$181.6213	$181.62	$181.60	$181.60
Purchase #6	$163.38	5.435%	$172.2597	$172.26	$172.25	$172.30
Purchase #7	$98.95	12.668%	$111.485	$111.49	$111.50	$111.50
7 purchase totals =	$1,016.51		$1,108.9920	$1,109.00	$1,109.00	$1,109.00