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	$62.89	3.435%	$65.0503	$65.05	$65.05	$65.10
Purchase #2	$160.78	9.738%	$176.4368	$176.44	$176.45	$176.40
Purchase #3	$155.57	10.829%	$172.4167	$172.42	$172.40	$172.40
Purchase #4	$236.81	7.180%	$253.813	$253.81	$253.80	$253.80
Purchase #5	$79.82	13.526%	$90.6165	$90.62	$90.60	$90.60
Purchase #6	$54.56	5.645%	$57.6399	$57.64	$57.65	$57.60
Purchase #7	$78.32	8.870%	$85.267	$85.27	$85.25	$85.30
7 purchase totals =	$828.75		$901.2402	$901.25	$901.20	$901.20