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	$99.27	10.255%	$109.4501	$109.45	$109.45	$109.50
Purchase #2	$229.86	5.639%	$242.8218	$242.82	$242.80	$242.80
Purchase #3	$5.72	7.486%	$6.1482	$6.15	$6.15	$6.10
Purchase #4	$242.89	4.781%	$254.5026	$254.50	$254.50	$254.50
Purchase #5	$143.75	10.508%	$158.8553	$158.86	$158.85	$158.90
Purchase #6	$144.95	9.580%	$158.8362	$158.84	$158.85	$158.80
Purchase #7	$45.27	5.476%	$47.749	$47.75	$47.75	$47.70
7 purchase totals =	$911.71		$978.3632	$978.37	$978.35	$978.30