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	$56.69	10.614%	$62.7071	$62.71	$62.70	$62.70
Purchase #2	$71.32	10.225%	$78.6125	$78.61	$78.60	$78.60
Purchase #3	$87.39	13.784%	$99.4358	$99.44	$99.45	$99.40
Purchase #4	$99.65	7.725%	$107.348	$107.35	$107.35	$107.30
Purchase #5	$205.72	11.681%	$229.7502	$229.75	$229.75	$229.80
Purchase #6	$226.64	12.215%	$254.3241	$254.32	$254.30	$254.30
Purchase #7	$137.80	5.551%	$145.4493	$145.45	$145.45	$145.40
7 purchase totals =	$885.21		$977.6270	$977.63	$977.60	$977.50