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	$112.28	13.575%	$127.522	$127.52	$127.50	$127.50
Purchase #2	$146.64	8.167%	$158.6161	$158.62	$158.60	$158.60
Purchase #3	$107.36	3.742%	$111.3774	$111.38	$111.40	$111.40
Purchase #4	$150.74	3.179%	$155.532	$155.53	$155.55	$155.50
Purchase #5	$183.78	7.810%	$198.1332	$198.13	$198.15	$198.10
Purchase #6	$37.68	7.862%	$40.6424	$40.64	$40.65	$40.60
Purchase #7	$112.38	3.723%	$116.5639	$116.56	$116.55	$116.60
7 purchase totals =	$850.86		$908.3870	$908.38	$908.40	$908.30