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	$69.82	9.514%	$76.4627	$76.46	$76.45	$76.50
Purchase #2	$42.31	12.191%	$47.468	$47.47	$47.45	$47.50
Purchase #3	$48.36	6.823%	$51.6596	$51.66	$51.65	$51.70
Purchase #4	$38.32	13.219%	$43.3855	$43.39	$43.40	$43.40
Purchase #5	$90.40	10.451%	$99.8477	$99.85	$99.85	$99.80
Purchase #6	$10.45	5.672%	$11.0427	$11.04	$11.05	$11.00
Purchase #7	$137.66	13.107%	$155.7031	$155.70	$155.70	$155.70
7 purchase totals =	$437.32		$485.5693	$485.57	$485.55	$485.60