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	$90.28	4.620%	$94.4509	$94.45	$94.45	$94.50
Purchase #2	$95.29	6.481%	$101.4657	$101.47	$101.45	$101.50
Purchase #3	$116.38	13.300%	$131.8585	$131.86	$131.85	$131.90
Purchase #4	$180.99	9.723%	$198.5877	$198.59	$198.60	$198.60
Purchase #5	$128.39	4.668%	$134.3832	$134.38	$134.40	$134.40
Purchase #6	$9.49	10.409%	$10.4778	$10.48	$10.50	$10.50
Purchase #7	$164.90	5.144%	$173.3825	$173.38	$173.40	$173.40
7 purchase totals =	$785.72		$844.6063	$844.61	$844.65	$844.80