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	$233.91	8.859%	$254.6321	$254.63	$254.65	$254.60
Purchase #2	$244.66	13.663%	$278.0879	$278.09	$278.10	$278.10
Purchase #3	$33.82	10.231%	$37.2801	$37.28	$37.30	$37.30
Purchase #4	$127.85	7.179%	$137.0284	$137.03	$137.05	$137.00
Purchase #5	$48.45	10.116%	$53.3512	$53.35	$53.35	$53.40
Purchase #6	$120.68	13.416%	$136.8704	$136.87	$136.85	$136.90
Purchase #7	$110.55	8.181%	$119.5941	$119.59	$119.60	$119.60
7 purchase totals =	$919.92		$1,016.8442	$1,016.84	$1,016.90	$1,016.90