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	$102.67	8.375%	$111.2686	$111.27	$111.25	$111.30
Purchase #2	$187.30	11.347%	$208.5529	$208.55	$208.55	$208.60
Purchase #3	$101.69	8.521%	$110.355	$110.36	$110.35	$110.40
Purchase #4	$71.85	9.485%	$78.665	$78.67	$78.65	$78.70
Purchase #5	$209.28	10.244%	$230.7186	$230.72	$230.70	$230.70
Purchase #6	$7.62	4.161%	$7.9371	$7.94	$7.95	$7.90
Purchase #7	$58.28	13.797%	$66.3209	$66.32	$66.30	$66.30
7 purchase totals =	$738.69		$813.8181	$813.83	$813.75	$813.90