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	$164.94	8.827%	$179.4993	$179.50	$179.50	$179.50
Purchase #2	$64.69	10.773%	$71.6591	$71.66	$71.65	$71.70
Purchase #3	$245.66	10.707%	$271.9628	$271.96	$271.95	$272.00
Purchase #4	$242.42	8.254%	$262.4293	$262.43	$262.45	$262.40
Purchase #5	$176.35	9.402%	$192.9304	$192.93	$192.95	$192.90
Purchase #6	$116.59	3.545%	$120.7231	$120.72	$120.70	$120.70
Purchase #7	$105.77	5.814%	$111.9195	$111.92	$111.90	$111.90
7 purchase totals =	$1,116.42		$1,211.1235	$1,211.12	$1,211.10	$1,211.10