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	$236.61	5.721%	$250.1465	$250.15	$250.15	$250.10
Purchase #2	$70.46	5.257%	$74.1641	$74.16	$74.15	$74.20
Purchase #3	$101.91	9.163%	$111.248	$111.25	$111.25	$111.20
Purchase #4	$58.77	4.252%	$61.2689	$61.27	$61.25	$61.30
Purchase #5	$173.57	7.816%	$187.1362	$187.14	$187.15	$187.10
Purchase #6	$156.58	11.597%	$174.7386	$174.74	$174.75	$174.70
Purchase #7	$248.55	4.152%	$258.8698	$258.87	$258.85	$258.90
7 purchase totals =	$1,046.45		$1,117.5721	$1,117.58	$1,117.55	$1,117.50