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	$104.49	6.565%	$111.3498	$111.35	$111.35	$111.30
Purchase #2	$129.56	10.362%	$142.985	$142.99	$143.00	$143.00
Purchase #3	$47.55	3.811%	$49.3621	$49.36	$49.35	$49.40
Purchase #4	$155.65	6.475%	$165.7283	$165.73	$165.75	$165.70
Purchase #5	$73.29	8.577%	$79.5761	$79.58	$79.60	$79.60
Purchase #6	$246.99	11.530%	$275.4679	$275.47	$275.45	$275.50
Purchase #7	$127.60	3.120%	$131.5811	$131.58	$131.60	$131.60
7 purchase totals =	$885.13		$956.0503	$956.06	$956.10	$956.10