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	$145.55	13.717%	$165.5151	$165.52	$165.50	$165.50
Purchase #2	$221.80	3.363%	$229.2591	$229.26	$229.25	$229.30
Purchase #3	$68.75	6.857%	$73.4642	$73.46	$73.45	$73.50
Purchase #4	$40.96	12.608%	$46.1242	$46.12	$46.10	$46.10
Purchase #5	$19.77	3.495%	$20.461	$20.46	$20.45	$20.50
Purchase #6	$21.49	13.767%	$24.4485	$24.45	$24.45	$24.40
Purchase #7	$153.94	9.175%	$168.064	$168.06	$168.05	$168.10
7 purchase totals =	$672.26		$727.3361	$727.33	$727.25	$727.40