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	$172.56	5.207%	$181.5452	$181.55	$181.55	$181.50
Purchase #2	$202.53	8.787%	$220.3263	$220.33	$220.35	$220.30
Purchase #3	$12.30	7.514%	$13.2242	$13.22	$13.20	$13.20
Purchase #4	$32.45	8.274%	$35.1349	$35.13	$35.15	$35.10
Purchase #5	$176.71	7.741%	$190.3891	$190.39	$190.40	$190.40
Purchase #6	$139.36	4.802%	$146.0521	$146.05	$146.05	$146.10
Purchase #7	$103.81	7.333%	$111.4224	$111.42	$111.40	$111.40
7 purchase totals =	$839.72		$898.0942	$898.09	$898.10	$898.00