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	$138.36	10.486%	$152.8684	$152.87	$152.85	$152.90
Purchase #2	$12.84	12.561%	$14.4528	$14.45	$14.45	$14.50
Purchase #3	$217.92	9.402%	$238.4088	$238.41	$238.40	$238.40
Purchase #4	$166.45	3.533%	$172.3307	$172.33	$172.35	$172.30
Purchase #5	$114.68	7.146%	$122.875	$122.88	$122.90	$122.90
Purchase #6	$118.89	7.220%	$127.4739	$127.47	$127.45	$127.50
Purchase #7	$235.89	6.208%	$250.5341	$250.53	$250.55	$250.50
7 purchase totals =	$1,005.03		$1,078.9437	$1,078.94	$1,078.95	$1,079.00