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	$38.64	11.688%	$43.1562	$43.16	$43.15	$43.20
Purchase #2	$191.42	12.723%	$215.7744	$215.77	$215.75	$215.80
Purchase #3	$103.64	7.352%	$111.2596	$111.26	$111.25	$111.30
Purchase #4	$69.27	6.609%	$73.8481	$73.85	$73.85	$73.80
Purchase #5	$11.51	11.462%	$12.8293	$12.83	$12.85	$12.80
Purchase #6	$153.62	10.456%	$169.6825	$169.68	$169.70	$169.70
Purchase #7	$92.89	5.527%	$98.024	$98.02	$98.00	$98.00
7 purchase totals =	$660.99		$724.5741	$724.57	$724.55	$724.60