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	$67.63	10.408%	$74.6689	$74.67	$74.65	$74.70
Purchase #2	$196.83	9.420%	$215.3714	$215.37	$215.35	$215.40
Purchase #3	$193.47	11.287%	$215.307	$215.31	$215.30	$215.30
Purchase #4	$104.52	6.773%	$111.5991	$111.60	$111.60	$111.60
Purchase #5	$38.83	4.116%	$40.4282	$40.43	$40.45	$40.40
Purchase #6	$245.28	13.415%	$278.1843	$278.18	$278.20	$278.20
Purchase #7	$206.45	4.444%	$215.6246	$215.62	$215.60	$215.60
7 purchase totals =	$1,053.01		$1,151.1835	$1,151.18	$1,151.15	$1,151.20