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	$151.76	8.852%	$165.1938	$165.19	$165.20	$165.20
Purchase #2	$145.65	13.473%	$165.2734	$165.27	$165.25	$165.30
Purchase #3	$170.80	5.111%	$179.5296	$179.53	$179.55	$179.50
Purchase #4	$69.60	3.133%	$71.7806	$71.78	$71.80	$71.80
Purchase #5	$71.66	6.146%	$76.0642	$76.06	$76.05	$76.10
Purchase #6	$14.61	4.244%	$15.23	$15.23	$15.25	$15.20
Purchase #7	$149.49	8.617%	$162.3716	$162.37	$162.35	$162.40
7 purchase totals =	$773.57		$835.4432	$835.43	$835.45	$835.50