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	$166.31	9.534%	$182.166	$182.17	$182.15	$182.20
Purchase #2	$173.56	5.374%	$182.8871	$182.89	$182.90	$182.90
Purchase #3	$13.95	12.734%	$15.7264	$15.73	$15.75	$15.70
Purchase #4	$141.29	10.684%	$156.3854	$156.39	$156.40	$156.40
Purchase #5	$46.51	5.190%	$48.9239	$48.92	$48.90	$48.90
Purchase #6	$248.84	5.468%	$262.4466	$262.45	$262.45	$262.40
Purchase #7	$104.90	6.437%	$111.6524	$111.65	$111.65	$111.70
7 purchase totals =	$895.36		$960.1878	$960.20	$960.20	$960.20