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	$220.91	10.537%	$244.1873	$244.19	$244.20	$244.20
Purchase #2	$198.88	9.643%	$218.058	$218.06	$218.05	$218.10
Purchase #3	$137.72	12.670%	$155.1691	$155.17	$155.15	$155.20
Purchase #4	$210.73	3.395%	$217.8843	$217.88	$217.90	$217.90
Purchase #5	$44.52	3.414%	$46.0399	$46.04	$46.05	$46.00
Purchase #6	$111.96	13.499%	$127.0735	$127.07	$127.05	$127.10
Purchase #7	$92.47	7.794%	$99.6771	$99.68	$99.70	$99.70
7 purchase totals =	$1,017.19		$1,108.0892	$1,108.09	$1,108.10	$1,108.20