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	$229.29	8.569%	$248.9379	$248.94	$248.95	$248.90
Purchase #2	$16.43	3.668%	$17.0327	$17.03	$17.05	$17.00
Purchase #3	$176.55	13.539%	$200.4531	$200.45	$200.45	$200.50
Purchase #4	$35.42	7.177%	$37.9621	$37.96	$37.95	$38.00
Purchase #5	$149.38	8.109%	$161.4932	$161.49	$161.50	$161.50
Purchase #6	$71.40	10.567%	$78.9448	$78.94	$78.95	$78.90
Purchase #7	$242.75	5.518%	$256.1449	$256.14	$256.15	$256.10
7 purchase totals =	$921.22		$1,000.9687	$1,000.95	$1,001.00	$1,000.90