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	$222.83	11.340%	$248.0989	$248.10	$248.10	$248.10
Purchase #2	$151.99	4.239%	$158.4329	$158.43	$158.45	$158.40
Purchase #3	$152.60	8.341%	$165.3284	$165.33	$165.35	$165.30
Purchase #4	$27.38	11.468%	$30.5199	$30.52	$30.50	$30.50
Purchase #5	$82.25	6.274%	$87.4104	$87.41	$87.40	$87.40
Purchase #6	$69.89	12.604%	$78.6989	$78.70	$78.70	$78.70
Purchase #7	$18.35	9.269%	$20.0509	$20.05	$20.05	$20.10
7 purchase totals =	$725.29		$788.5403	$788.54	$788.55	$788.50