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	$12.81	13.505%	$14.54	$14.54	$14.55	$14.50
Purchase #2	$179.46	8.258%	$194.2798	$194.28	$194.30	$194.30
Purchase #3	$133.32	13.243%	$150.9756	$150.98	$151.00	$151.00
Purchase #4	$137.77	7.815%	$148.5367	$148.54	$148.55	$148.50
Purchase #5	$128.52	3.605%	$133.1531	$133.15	$133.15	$133.20
Purchase #6	$100.55	13.632%	$114.257	$114.26	$114.25	$114.30
Purchase #7	$50.88	13.216%	$57.6043	$57.60	$57.60	$57.60
7 purchase totals =	$743.31		$813.3465	$813.35	$813.40	$813.40