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	$105.27	6.259%	$111.8588	$111.86	$111.85	$111.90
Purchase #2	$164.55	13.453%	$186.6869	$186.69	$186.70	$186.70
Purchase #3	$228.43	10.380%	$252.141	$252.14	$252.15	$252.10
Purchase #4	$183.36	7.609%	$197.3119	$197.31	$197.30	$197.30
Purchase #5	$241.28	3.831%	$250.5234	$250.52	$250.50	$250.50
Purchase #6	$164.59	12.574%	$185.2855	$185.29	$185.30	$185.30
Purchase #7	$212.77	11.250%	$236.7066	$236.71	$236.70	$236.70
7 purchase totals =	$1,300.25		$1,420.5141	$1,420.52	$1,420.50	$1,420.50