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	$99.60	11.592%	$111.1456	$111.15	$111.15	$111.10
Purchase #2	$185.31	5.806%	$196.0691	$196.07	$196.05	$196.10
Purchase #3	$132.53	7.541%	$142.5241	$142.52	$142.50	$142.50
Purchase #4	$142.61	8.761%	$155.1041	$155.10	$155.10	$155.10
Purchase #5	$46.96	10.551%	$51.9147	$51.91	$51.90	$51.90
Purchase #6	$138.44	3.525%	$143.32	$143.32	$143.30	$143.30
Purchase #7	$69.56	3.626%	$72.0822	$72.08	$72.10	$72.10
7 purchase totals =	$815.01		$872.1598	$872.15	$872.10	$872.10