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	$69.26	4.733%	$72.5381	$72.54	$72.55	$72.50
Purchase #2	$32.60	6.789%	$34.8132	$34.81	$34.80	$34.80
Purchase #3	$130.31	13.868%	$148.3814	$148.38	$148.40	$148.40
Purchase #4	$205.47	8.564%	$223.0665	$223.07	$223.05	$223.10
Purchase #5	$49.87	6.766%	$53.2442	$53.24	$53.25	$53.20
Purchase #6	$104.55	11.520%	$116.5942	$116.59	$116.60	$116.60
Purchase #7	$234.84	4.217%	$244.7432	$244.74	$244.75	$244.70
7 purchase totals =	$826.90		$893.3808	$893.37	$893.40	$893.30