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	$137.47	10.175%	$151.4576	$151.46	$151.45	$151.50
Purchase #2	$105.71	6.870%	$112.9723	$112.97	$112.95	$113.00
Purchase #3	$47.90	9.497%	$52.4491	$52.45	$52.45	$52.40
Purchase #4	$95.51	5.833%	$101.0811	$101.08	$101.10	$101.10
Purchase #5	$39.61	5.490%	$41.7846	$41.78	$41.80	$41.80
Purchase #6	$187.84	9.377%	$205.4538	$205.45	$205.45	$205.50
Purchase #7	$78.43	5.173%	$82.4872	$82.49	$82.50	$82.50
7 purchase totals =	$692.47		$747.6857	$747.68	$747.70	$747.80