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	$42.63	13.758%	$48.495	$48.50	$48.50	$48.50
Purchase #2	$65.58	9.614%	$71.8849	$71.88	$71.90	$71.90
Purchase #3	$235.32	7.441%	$252.8302	$252.83	$252.85	$252.80
Purchase #4	$240.54	11.514%	$268.2358	$268.24	$268.25	$268.20
Purchase #5	$100.58	11.728%	$112.376	$112.38	$112.40	$112.40
Purchase #6	$149.25	4.202%	$155.5215	$155.52	$155.50	$155.50
Purchase #7	$234.60	9.307%	$256.4342	$256.43	$256.45	$256.40
7 purchase totals =	$1,068.50		$1,165.7776	$1,165.78	$1,165.85	$1,165.70