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	$13.32	12.238%	$14.9501	$14.95	$14.95	$15.00
Purchase #2	$225.30	12.842%	$254.233	$254.23	$254.25	$254.20
Purchase #3	$78.68	5.771%	$83.2206	$83.22	$83.20	$83.20
Purchase #4	$41.83	13.470%	$47.4645	$47.46	$47.45	$47.50
Purchase #5	$117.59	8.676%	$127.7921	$127.79	$127.80	$127.80
Purchase #6	$69.73	3.482%	$72.158	$72.16	$72.15	$72.20
Purchase #7	$207.73	8.523%	$225.4348	$225.43	$225.45	$225.40
7 purchase totals =	$754.18		$825.2531	$825.24	$825.25	$825.30