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	$89.44	12.317%	$100.4563	$100.46	$100.45	$100.50
Purchase #2	$104.73	10.852%	$116.0953	$116.10	$116.10	$116.10
Purchase #3	$144.46	10.841%	$160.1209	$160.12	$160.10	$160.10
Purchase #4	$150.60	8.757%	$163.788	$163.79	$163.80	$163.80
Purchase #5	$145.75	4.591%	$152.4414	$152.44	$152.45	$152.40
Purchase #6	$79.69	3.485%	$82.4672	$82.47	$82.45	$82.50
Purchase #7	$97.30	4.692%	$101.8653	$101.87	$101.85	$101.90
7 purchase totals =	$811.97		$877.2344	$877.25	$877.20	$877.30