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	$142.41	11.557%	$158.8683	$158.87	$158.85	$158.90
Purchase #2	$47.87	10.575%	$52.9323	$52.93	$52.95	$52.90
Purchase #3	$148.67	12.681%	$167.5228	$167.52	$167.50	$167.50
Purchase #4	$65.66	7.230%	$70.4072	$70.41	$70.40	$70.40
Purchase #5	$62.82	7.768%	$67.6999	$67.70	$67.70	$67.70
Purchase #6	$175.49	10.113%	$193.2373	$193.24	$193.25	$193.20
Purchase #7	$92.94	11.598%	$103.7192	$103.72	$103.70	$103.70
7 purchase totals =	$735.86		$814.3870	$814.39	$814.35	$814.30