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	$166.62	3.380%	$172.2518	$172.25	$172.25	$172.30
Purchase #2	$9.89	5.699%	$10.4536	$10.45	$10.45	$10.50
Purchase #3	$109.99	6.353%	$116.9777	$116.98	$117.00	$117.00
Purchase #4	$82.85	8.363%	$89.7787	$89.78	$89.80	$89.80
Purchase #5	$179.49	11.857%	$200.7721	$200.77	$200.75	$200.80
Purchase #6	$60.72	7.575%	$65.3195	$65.32	$65.30	$65.30
Purchase #7	$50.80	7.864%	$54.7949	$54.79	$54.80	$54.80
7 purchase totals =	$660.36		$710.3483	$710.34	$710.35	$710.50