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	$215.47	8.711%	$234.2396	$234.24	$234.25	$234.20
Purchase #2	$32.37	4.468%	$33.8163	$33.82	$33.80	$33.80
Purchase #3	$70.84	13.239%	$80.2185	$80.22	$80.20	$80.20
Purchase #4	$241.68	3.670%	$250.5497	$250.55	$250.55	$250.50
Purchase #5	$185.44	5.123%	$194.9401	$194.94	$194.95	$194.90
Purchase #6	$198.61	8.835%	$216.1572	$216.16	$216.15	$216.20
Purchase #7	$48.29	7.109%	$51.7229	$51.72	$51.70	$51.70
7 purchase totals =	$992.70		$1,061.6443	$1,061.65	$1,061.60	$1,061.50