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	$173.76	5.752%	$183.7547	$183.75	$183.75	$183.80
Purchase #2	$217.85	4.695%	$228.0781	$228.08	$228.10	$228.10
Purchase #3	$51.66	3.832%	$53.6396	$53.64	$53.65	$53.60
Purchase #4	$183.62	8.114%	$198.5189	$198.52	$198.50	$198.50
Purchase #5	$102.85	8.464%	$111.5552	$111.56	$111.55	$111.60
Purchase #6	$166.87	4.357%	$174.1405	$174.14	$174.15	$174.10
Purchase #7	$78.84	12.215%	$88.4703	$88.47	$88.45	$88.50
7 purchase totals =	$975.45		$1,038.1573	$1,038.16	$1,038.15	$1,038.20