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	$138.25	6.153%	$146.7565	$146.76	$146.75	$146.80
Purchase #2	$153.69	3.422%	$158.9493	$158.95	$158.95	$158.90
Purchase #3	$145.75	11.771%	$162.9062	$162.91	$162.90	$162.90
Purchase #4	$103.57	11.800%	$115.7913	$115.79	$115.80	$115.80
Purchase #5	$127.85	13.336%	$144.9001	$144.90	$144.90	$144.90
Purchase #6	$228.74	11.597%	$255.267	$255.27	$255.25	$255.30
Purchase #7	$119.47	7.156%	$128.0193	$128.02	$128.00	$128.00
7 purchase totals =	$1,017.32		$1,112.5897	$1,112.60	$1,112.55	$1,112.60