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	$98.59	9.861%	$108.312	$108.31	$108.30	$108.30
Purchase #2	$195.60	13.244%	$221.5053	$221.51	$221.50	$221.50
Purchase #3	$37.92	13.806%	$43.1552	$43.16	$43.15	$43.20
Purchase #4	$188.45	4.470%	$196.8737	$196.87	$196.85	$196.90
Purchase #5	$71.87	5.306%	$75.6834	$75.68	$75.70	$75.70
Purchase #6	$69.89	9.328%	$76.4093	$76.41	$76.40	$76.40
Purchase #7	$51.83	3.436%	$53.6109	$53.61	$53.60	$53.60
7 purchase totals =	$714.15		$775.5498	$775.55	$775.50	$775.60