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	$234.50	4.422%	$244.8696	$244.87	$244.85	$244.90
Purchase #2	$245.96	8.422%	$266.6748	$266.67	$266.65	$266.70
Purchase #3	$59.29	6.704%	$63.2648	$63.26	$63.25	$63.30
Purchase #4	$100.96	9.325%	$110.3745	$110.37	$110.35	$110.40
Purchase #5	$55.41	10.102%	$61.0075	$61.01	$61.00	$61.00
Purchase #6	$59.55	8.565%	$64.6505	$64.65	$64.65	$64.70
Purchase #7	$178.27	7.401%	$191.4638	$191.46	$191.45	$191.50
7 purchase totals =	$933.94		$1,002.3055	$1,002.29	$1,002.20	$1,002.50