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	$207.36	11.357%	$230.9099	$230.91	$230.90	$230.90
Purchase #2	$52.62	9.263%	$57.4942	$57.49	$57.50	$57.50
Purchase #3	$151.35	7.513%	$162.7209	$162.72	$162.70	$162.70
Purchase #4	$249.43	9.213%	$272.41	$272.41	$272.40	$272.40
Purchase #5	$209.68	11.173%	$233.1075	$233.11	$233.10	$233.10
Purchase #6	$106.73	4.816%	$111.8701	$111.87	$111.85	$111.90
Purchase #7	$40.79	6.322%	$43.3687	$43.37	$43.35	$43.40
7 purchase totals =	$1,017.96		$1,111.8813	$1,111.88	$1,111.80	$1,111.90