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	$228.32	11.212%	$253.9192	$253.92	$253.90	$253.90
Purchase #2	$114.50	4.350%	$119.4808	$119.48	$119.50	$119.50
Purchase #3	$77.51	4.682%	$81.139	$81.14	$81.15	$81.10
Purchase #4	$203.76	13.163%	$230.5809	$230.58	$230.60	$230.60
Purchase #5	$111.86	10.399%	$123.4923	$123.49	$123.50	$123.50
Purchase #6	$147.75	5.550%	$155.9501	$155.95	$155.95	$156.00
Purchase #7	$178.71	9.691%	$196.0288	$196.03	$196.05	$196.00
7 purchase totals =	$1,062.41		$1,160.5911	$1,160.59	$1,160.65	$1,160.60