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	$103.90	7.202%	$111.3829	$111.38	$111.40	$111.40
Purchase #2	$156.25	5.528%	$164.8875	$164.89	$164.90	$164.90
Purchase #3	$97.74	5.503%	$103.1186	$103.12	$103.10	$103.10
Purchase #4	$149.84	10.506%	$165.5822	$165.58	$165.60	$165.60
Purchase #5	$214.68	7.856%	$231.5453	$231.55	$231.55	$231.50
Purchase #6	$189.63	4.608%	$198.3682	$198.37	$198.35	$198.40
Purchase #7	$246.32	3.202%	$254.2072	$254.21	$254.20	$254.20
7 purchase totals =	$1,158.36		$1,229.0919	$1,229.10	$1,229.10	$1,229.10