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	$160.61	8.712%	$174.6023	$174.60	$174.60	$174.60
Purchase #2	$116.98	9.181%	$127.7199	$127.72	$127.70	$127.70
Purchase #3	$106.62	10.850%	$118.1883	$118.19	$118.20	$118.20
Purchase #4	$217.55	6.380%	$231.4297	$231.43	$231.45	$231.40
Purchase #5	$135.68	6.275%	$144.1939	$144.19	$144.20	$144.20
Purchase #6	$62.80	13.263%	$71.1292	$71.13	$71.15	$71.10
Purchase #7	$130.39	12.391%	$146.5466	$146.55	$146.55	$146.50
7 purchase totals =	$930.63		$1,013.8099	$1,013.81	$1,013.85	$1,013.70