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	$88.40	13.207%	$100.075	$100.08	$100.10	$100.10
Purchase #2	$16.70	3.206%	$17.2354	$17.24	$17.25	$17.20
Purchase #3	$168.79	4.218%	$175.9096	$175.91	$175.90	$175.90
Purchase #4	$159.79	13.176%	$180.8439	$180.84	$180.85	$180.80
Purchase #5	$118.29	7.559%	$127.2315	$127.23	$127.25	$127.20
Purchase #6	$148.28	8.168%	$160.3915	$160.39	$160.40	$160.40
Purchase #7	$241.51	6.602%	$257.4545	$257.45	$257.45	$257.50
7 purchase totals =	$941.76		$1,019.1414	$1,019.14	$1,019.20	$1,019.10