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	$56.81	10.756%	$62.9205	$62.92	$62.90	$62.90
Purchase #2	$117.70	11.550%	$131.2944	$131.29	$131.30	$131.30
Purchase #3	$157.99	12.233%	$177.3169	$177.32	$177.30	$177.30
Purchase #4	$89.78	7.118%	$96.1705	$96.17	$96.15	$96.20
Purchase #5	$238.87	3.245%	$246.6213	$246.62	$246.60	$246.60
Purchase #6	$127.61	5.704%	$134.8889	$134.89	$134.90	$134.90
Purchase #7	$79.78	13.154%	$90.2743	$90.27	$90.25	$90.30
7 purchase totals =	$868.54		$939.4868	$939.48	$939.40	$939.50