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	$194.88	13.656%	$221.4928	$221.49	$221.50	$221.50
Purchase #2	$58.68	4.815%	$61.5054	$61.51	$61.50	$61.50
Purchase #3	$111.71	12.675%	$125.8692	$125.87	$125.85	$125.90
Purchase #4	$130.38	11.745%	$145.6931	$145.69	$145.70	$145.70
Purchase #5	$89.47	12.419%	$100.5813	$100.58	$100.60	$100.60
Purchase #6	$202.85	8.648%	$220.3925	$220.39	$220.40	$220.40
Purchase #7	$180.80	13.776%	$205.707	$205.71	$205.70	$205.70
7 purchase totals =	$968.77		$1,081.2413	$1,081.24	$1,081.25	$1,081.30