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	$120.47	9.633%	$132.0749	$132.07	$132.05	$132.10
Purchase #2	$184.61	9.407%	$201.9763	$201.98	$202.00	$202.00
Purchase #3	$233.97	11.747%	$261.4545	$261.45	$261.45	$261.50
Purchase #4	$111.33	5.480%	$117.4309	$117.43	$117.45	$117.40
Purchase #5	$116.51	9.219%	$127.2511	$127.25	$127.25	$127.30
Purchase #6	$158.95	8.548%	$172.537	$172.54	$172.55	$172.50
Purchase #7	$127.78	3.254%	$131.938	$131.94	$131.95	$131.90
7 purchase totals =	$1,053.62		$1,144.6627	$1,144.66	$1,144.70	$1,144.70