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	$64.75	8.501%	$70.2544	$70.25	$70.25	$70.30
Purchase #2	$86.67	4.865%	$90.8865	$90.89	$90.90	$90.90
Purchase #3	$209.33	5.820%	$221.513	$221.51	$221.50	$221.50
Purchase #4	$10.97	5.719%	$11.5974	$11.60	$11.60	$11.60
Purchase #5	$104.81	6.306%	$111.4193	$111.42	$111.40	$111.40
Purchase #6	$59.36	6.378%	$63.146	$63.15	$63.15	$63.10
Purchase #7	$112.25	5.870%	$118.8391	$118.84	$118.85	$118.80
7 purchase totals =	$648.14		$687.6557	$687.66	$687.65	$687.60