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	$237.61	10.124%	$261.6656	$261.67	$261.65	$261.70
Purchase #2	$100.28	11.127%	$111.4382	$111.44	$111.45	$111.40
Purchase #3	$123.59	3.375%	$127.7612	$127.76	$127.75	$127.80
Purchase #4	$9.32	8.227%	$10.0868	$10.09	$10.10	$10.10
Purchase #5	$18.76	3.272%	$19.3738	$19.37	$19.35	$19.40
Purchase #6	$143.85	11.522%	$160.4244	$160.42	$160.40	$160.40
Purchase #7	$226.41	6.153%	$240.341	$240.34	$240.35	$240.30
7 purchase totals =	$859.82		$931.0910	$931.09	$931.05	$931.10