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	$123.68	8.188%	$133.8069	$133.81	$133.80	$133.80
Purchase #2	$40.47	6.536%	$43.1151	$43.12	$43.10	$43.10
Purchase #3	$119.38	10.448%	$131.8528	$131.85	$131.85	$131.90
Purchase #4	$106.88	4.708%	$111.9119	$111.91	$111.90	$111.90
Purchase #5	$235.61	13.419%	$267.2265	$267.23	$267.25	$267.20
Purchase #6	$163.25	6.842%	$174.4196	$174.42	$174.40	$174.40
Purchase #7	$225.62	12.567%	$253.9737	$253.97	$253.95	$254.00
7 purchase totals =	$1,014.89		$1,116.3065	$1,116.31	$1,116.25	$1,116.30