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	$65.35	11.398%	$72.7986	$72.80	$72.80	$72.80
Purchase #2	$32.38	9.455%	$35.4415	$35.44	$35.45	$35.40
Purchase #3	$229.45	5.110%	$241.1749	$241.17	$241.15	$241.20
Purchase #4	$230.95	13.737%	$262.6756	$262.68	$262.70	$262.70
Purchase #5	$172.94	13.361%	$196.0465	$196.05	$196.05	$196.00
Purchase #6	$104.64	11.277%	$116.4403	$116.44	$116.45	$116.40
Purchase #7	$223.71	3.103%	$230.6517	$230.65	$230.65	$230.70
7 purchase totals =	$1,059.42		$1,155.2291	$1,155.23	$1,155.25	$1,155.20