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	$113.54	4.278%	$118.3972	$118.40	$118.40	$118.40
Purchase #2	$101.38	11.312%	$112.8481	$112.85	$112.85	$112.80
Purchase #3	$173.29	10.557%	$191.5842	$191.58	$191.60	$191.60
Purchase #4	$175.88	11.774%	$196.5881	$196.59	$196.60	$196.60
Purchase #5	$26.77	4.595%	$28.0001	$28.00	$28.00	$28.00
Purchase #6	$190.71	3.372%	$197.1407	$197.14	$197.15	$197.10
Purchase #7	$237.37	10.420%	$262.104	$262.10	$262.10	$262.10
7 purchase totals =	$1,018.94		$1,106.6624	$1,106.66	$1,106.70	$1,106.60