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	$230.52	11.860%	$257.8597	$257.86	$257.85	$257.90
Purchase #2	$95.86	5.272%	$100.9137	$100.91	$100.90	$100.90
Purchase #3	$119.66	8.675%	$130.0405	$130.04	$130.05	$130.00
Purchase #4	$205.93	10.849%	$228.2713	$228.27	$228.25	$228.30
Purchase #5	$164.48	4.805%	$172.3833	$172.38	$172.40	$172.40
Purchase #6	$224.33	11.114%	$249.262	$249.26	$249.25	$249.30
Purchase #7	$31.64	8.193%	$34.2323	$34.23	$34.25	$34.20
7 purchase totals =	$1,072.42		$1,172.9628	$1,172.95	$1,172.95	$1,173.00