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	$115.49	10.622%	$127.7573	$127.76	$127.75	$127.80
Purchase #2	$135.39	5.655%	$143.0463	$143.05	$143.05	$143.00
Purchase #3	$181.58	12.846%	$204.9058	$204.91	$204.90	$204.90
Purchase #4	$31.49	11.406%	$35.0817	$35.08	$35.10	$35.10
Purchase #5	$184.31	8.777%	$200.4869	$200.49	$200.50	$200.50
Purchase #6	$56.62	5.659%	$59.8241	$59.82	$59.80	$59.80
Purchase #7	$162.73	6.343%	$173.052	$173.05	$173.05	$173.10
7 purchase totals =	$867.61		$944.1541	$944.16	$944.15	$944.20