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	$65.73	9.797%	$72.1696	$72.17	$72.15	$72.20
Purchase #2	$143.39	6.288%	$152.4064	$152.41	$152.40	$152.40
Purchase #3	$83.76	6.608%	$89.2949	$89.29	$89.30	$89.30
Purchase #4	$58.87	6.433%	$62.6571	$62.66	$62.65	$62.70
Purchase #5	$176.53	3.806%	$183.2487	$183.25	$183.25	$183.20
Purchase #6	$158.45	10.178%	$174.577	$174.58	$174.60	$174.60
Purchase #7	$51.85	9.548%	$56.8006	$56.80	$56.80	$56.80
7 purchase totals =	$738.58		$791.1543	$791.16	$791.15	$791.20