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	$158.96	8.622%	$172.6655	$172.67	$172.65	$172.70
Purchase #2	$176.47	12.540%	$198.5993	$198.60	$198.60	$198.60
Purchase #3	$95.45	13.412%	$108.2518	$108.25	$108.25	$108.30
Purchase #4	$58.51	4.523%	$61.1564	$61.16	$61.15	$61.20
Purchase #5	$228.30	6.201%	$242.4569	$242.46	$242.45	$242.50
Purchase #6	$48.25	10.526%	$53.3288	$53.33	$53.35	$53.30
Purchase #7	$249.89	9.210%	$272.9049	$272.90	$272.90	$272.90
7 purchase totals =	$1,015.83		$1,109.3636	$1,109.37	$1,109.35	$1,109.50