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	$163.75	9.526%	$179.3488	$179.35	$179.35	$179.30
Purchase #2	$41.55	4.631%	$43.4742	$43.47	$43.45	$43.50
Purchase #3	$64.78	10.469%	$71.5618	$71.56	$71.55	$71.60
Purchase #4	$208.32	12.106%	$233.5392	$233.54	$233.55	$233.50
Purchase #5	$76.64	11.211%	$85.2321	$85.23	$85.25	$85.20
Purchase #6	$17.88	6.849%	$19.1046	$19.10	$19.10	$19.10
Purchase #7	$155.69	11.554%	$173.6784	$173.68	$173.70	$173.70
7 purchase totals =	$728.61		$805.9391	$805.93	$805.95	$805.90