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	$8.63	9.514%	$9.4511	$9.45	$9.45	$9.50
Purchase #2	$105.41	8.255%	$114.1116	$114.11	$114.10	$114.10
Purchase #3	$35.86	3.589%	$37.147	$37.15	$37.15	$37.10
Purchase #4	$81.40	13.380%	$92.2913	$92.29	$92.30	$92.30
Purchase #5	$165.79	5.142%	$174.3149	$174.31	$174.30	$174.30
Purchase #6	$7.52	5.683%	$7.9474	$7.95	$7.95	$7.90
Purchase #7	$58.43	11.821%	$65.337	$65.34	$65.35	$65.30
7 purchase totals =	$463.04		$500.6003	$500.60	$500.60	$500.50