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	$6.92	4.818%	$7.2534	$7.25	$7.25	$7.30
Purchase #2	$80.52	11.570%	$89.8362	$89.84	$89.85	$89.80
Purchase #3	$54.97	10.520%	$60.7528	$60.75	$60.75	$60.80
Purchase #4	$151.98	7.729%	$163.7265	$163.73	$163.75	$163.70
Purchase #5	$101.27	9.862%	$111.2572	$111.26	$111.25	$111.30
Purchase #6	$113.28	12.246%	$127.1523	$127.15	$127.15	$127.20
Purchase #7	$157.53	11.483%	$175.6192	$175.62	$175.60	$175.60
7 purchase totals =	$666.47		$735.5976	$735.60	$735.60	$735.70