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	$119.96	6.460%	$127.7094	$127.71	$127.70	$127.70
Purchase #2	$79.27	12.798%	$89.415	$89.42	$89.40	$89.40
Purchase #3	$170.27	3.698%	$176.5666	$176.57	$176.55	$176.60
Purchase #4	$9.97	11.775%	$11.144	$11.14	$11.15	$11.10
Purchase #5	$104.61	6.168%	$111.0623	$111.06	$111.05	$111.10
Purchase #6	$188.78	3.202%	$194.8247	$194.82	$194.80	$194.80
Purchase #7	$147.66	5.631%	$155.9747	$155.97	$155.95	$156.00
7 purchase totals =	$820.52		$866.6967	$866.69	$866.60	$866.70