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	$192.44	11.527%	$214.6226	$214.62	$214.60	$214.60
Purchase #2	$85.30	5.835%	$90.2773	$90.28	$90.30	$90.30
Purchase #3	$94.97	12.663%	$106.9961	$107.00	$107.00	$107.00
Purchase #4	$240.86	11.810%	$269.3056	$269.31	$269.30	$269.30
Purchase #5	$218.86	4.553%	$228.8247	$228.82	$228.80	$228.80
Purchase #6	$40.51	11.840%	$45.3064	$45.31	$45.30	$45.30
Purchase #7	$119.68	6.136%	$127.0236	$127.02	$127.00	$127.00
7 purchase totals =	$992.62		$1,082.3563	$1,082.36	$1,082.30	$1,082.30