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	$92.61	8.103%	$100.1142	$100.11	$100.10	$100.10
Purchase #2	$103.42	4.653%	$108.2321	$108.23	$108.25	$108.20
Purchase #3	$166.85	5.629%	$176.242	$176.24	$176.25	$176.20
Purchase #4	$125.94	3.447%	$130.2812	$130.28	$130.30	$130.30
Purchase #5	$33.67	3.541%	$34.8623	$34.86	$34.85	$34.90
Purchase #6	$166.36	11.126%	$184.8692	$184.87	$184.85	$184.90
Purchase #7	$196.83	7.429%	$211.4525	$211.45	$211.45	$211.50
7 purchase totals =	$885.68		$946.0535	$946.04	$946.05	$946.10