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	$112.65	13.262%	$127.5896	$127.59	$127.60	$127.60
Purchase #2	$226.33	13.296%	$256.4228	$256.42	$256.40	$256.40
Purchase #3	$141.77	6.657%	$151.2076	$151.21	$151.20	$151.20
Purchase #4	$240.72	11.842%	$269.2261	$269.23	$269.25	$269.20
Purchase #5	$183.81	8.151%	$198.7924	$198.79	$198.80	$198.80
Purchase #6	$207.73	7.431%	$223.1664	$223.17	$223.15	$223.20
Purchase #7	$52.55	9.648%	$57.62	$57.62	$57.60	$57.60
7 purchase totals =	$1,165.56		$1,284.0249	$1,284.03	$1,284.00	$1,284.00