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	$37.26	9.662%	$40.8601	$40.86	$40.85	$40.90
Purchase #2	$152.40	13.834%	$173.483	$173.48	$173.50	$173.50
Purchase #3	$250.35	4.624%	$261.9262	$261.93	$261.95	$261.90
Purchase #4	$188.55	4.463%	$196.965	$196.97	$196.95	$197.00
Purchase #5	$111.54	13.488%	$126.5845	$126.58	$126.60	$126.60
Purchase #6	$148.59	11.123%	$165.1177	$165.12	$165.10	$165.10
Purchase #7	$229.31	11.767%	$256.2929	$256.29	$256.30	$256.30
7 purchase totals =	$1,118.00		$1,221.2294	$1,221.23	$1,221.25	$1,221.30