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	$115.51	10.111%	$127.1892	$127.19	$127.20	$127.20
Purchase #2	$155.79	11.333%	$173.4457	$173.45	$173.45	$173.40
Purchase #3	$184.91	6.375%	$196.698	$196.70	$196.70	$196.70
Purchase #4	$213.29	10.423%	$235.5212	$235.52	$235.50	$235.50
Purchase #5	$145.30	8.781%	$158.0588	$158.06	$158.05	$158.10
Purchase #6	$12.71	7.710%	$13.6899	$13.69	$13.70	$13.70
Purchase #7	$128.54	4.344%	$134.1238	$134.12	$134.10	$134.10
7 purchase totals =	$956.05		$1,038.7266	$1,038.73	$1,038.70	$1,038.70