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	$44.81	6.812%	$47.8625	$47.86	$47.85	$47.90
Purchase #2	$38.75	7.429%	$41.6287	$41.63	$41.65	$41.60
Purchase #3	$107.58	3.430%	$111.27	$111.27	$111.25	$111.30
Purchase #4	$46.75	8.809%	$50.8682	$50.87	$50.85	$50.90
Purchase #5	$49.73	6.205%	$52.8157	$52.82	$52.80	$52.80
Purchase #6	$123.80	5.477%	$130.5805	$130.58	$130.60	$130.60
Purchase #7	$83.42	8.413%	$90.4381	$90.44	$90.45	$90.40
7 purchase totals =	$494.84		$525.4637	$525.47	$525.45	$525.50