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	$166.98	8.605%	$181.3486	$181.35	$181.35	$181.30
Purchase #2	$45.45	7.131%	$48.691	$48.69	$48.70	$48.70
Purchase #3	$165.89	11.849%	$185.5463	$185.55	$185.55	$185.50
Purchase #4	$160.43	12.723%	$180.8415	$180.84	$180.85	$180.80
Purchase #5	$34.97	7.339%	$37.5364	$37.54	$37.55	$37.50
Purchase #6	$206.92	11.593%	$230.9082	$230.91	$230.90	$230.90
Purchase #7	$48.51	12.127%	$54.3928	$54.39	$54.40	$54.40
7 purchase totals =	$829.15		$919.2648	$919.27	$919.30	$919.10