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	$90.32	7.205%	$96.8276	$96.83	$96.85	$96.80
Purchase #2	$205.40	6.256%	$218.2498	$218.25	$218.25	$218.20
Purchase #3	$47.64	10.400%	$52.5946	$52.59	$52.60	$52.60
Purchase #4	$112.59	3.847%	$116.9213	$116.92	$116.90	$116.90
Purchase #5	$110.80	3.528%	$114.709	$114.71	$114.70	$114.70
Purchase #6	$33.90	12.475%	$38.129	$38.13	$38.15	$38.10
Purchase #7	$50.74	5.796%	$53.6809	$53.68	$53.70	$53.70
7 purchase totals =	$651.39		$691.1122	$691.11	$691.15	$691.00