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	$57.72	13.178%	$65.3263	$65.33	$65.35	$65.30
Purchase #2	$182.99	4.540%	$191.2977	$191.30	$191.30	$191.30
Purchase #3	$176.40	12.542%	$198.5241	$198.52	$198.50	$198.50
Purchase #4	$89.39	3.861%	$92.8413	$92.84	$92.85	$92.80
Purchase #5	$136.83	5.806%	$144.7743	$144.77	$144.75	$144.80
Purchase #6	$230.83	12.773%	$260.3139	$260.31	$260.30	$260.30
Purchase #7	$111.61	3.810%	$115.8623	$115.86	$115.85	$115.90
7 purchase totals =	$985.77		$1,068.9399	$1,068.93	$1,068.90	$1,068.90