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	$234.28	11.412%	$261.016	$261.02	$261.00	$261.00
Purchase #2	$238.72	10.342%	$263.4084	$263.41	$263.40	$263.40
Purchase #3	$159.25	13.406%	$180.5991	$180.60	$180.60	$180.60
Purchase #4	$166.49	10.802%	$184.4742	$184.47	$184.45	$184.50
Purchase #5	$241.76	6.398%	$257.2278	$257.23	$257.25	$257.20
Purchase #6	$234.62	9.305%	$256.4514	$256.45	$256.45	$256.50
Purchase #7	$47.44	11.866%	$53.0692	$53.07	$53.05	$53.10
7 purchase totals =	$1,322.56		$1,456.2461	$1,456.25	$1,456.20	$1,456.30