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	$76.97	4.781%	$80.6499	$80.65	$80.65	$80.60
Purchase #2	$11.53	9.194%	$12.5901	$12.59	$12.60	$12.60
Purchase #3	$34.48	8.432%	$37.3874	$37.39	$37.40	$37.40
Purchase #4	$60.35	9.365%	$66.0018	$66.00	$66.00	$66.00
Purchase #5	$92.90	4.563%	$97.139	$97.14	$97.15	$97.10
Purchase #6	$100.58	10.621%	$111.2626	$111.26	$111.25	$111.30
Purchase #7	$155.44	12.368%	$174.6648	$174.66	$174.65	$174.70
7 purchase totals =	$532.25		$579.6956	$579.69	$579.70	$579.70