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	$109.39	6.546%	$116.5507	$116.55	$116.55	$116.60
Purchase #2	$141.80	4.185%	$147.7343	$147.73	$147.75	$147.70
Purchase #3	$160.85	7.139%	$172.3331	$172.33	$172.35	$172.30
Purchase #4	$141.32	9.240%	$154.378	$154.38	$154.40	$154.40
Purchase #5	$155.49	11.345%	$173.1303	$173.13	$173.15	$173.10
Purchase #6	$110.69	6.833%	$118.2534	$118.25	$118.25	$118.30
Purchase #7	$192.70	13.736%	$219.1693	$219.17	$219.15	$219.20
7 purchase totals =	$1,012.24		$1,101.5491	$1,101.54	$1,101.60	$1,101.60