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	$212.37	7.663%	$228.6439	$228.64	$228.65	$228.60
Purchase #2	$45.86	10.548%	$50.6973	$50.70	$50.70	$50.70
Purchase #3	$90.30	11.385%	$100.5807	$100.58	$100.60	$100.60
Purchase #4	$168.43	13.544%	$191.2422	$191.24	$191.25	$191.20
Purchase #5	$81.78	10.200%	$90.1216	$90.12	$90.10	$90.10
Purchase #6	$241.71	12.823%	$272.7045	$272.70	$272.70	$272.70
Purchase #7	$70.58	6.272%	$75.0068	$75.01	$75.00	$75.00
7 purchase totals =	$911.03		$1,008.9970	$1,008.99	$1,009.00	$1,008.90