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	$97.41	10.672%	$107.8056	$107.81	$107.80	$107.80
Purchase #2	$101.89	9.437%	$111.5054	$111.51	$111.50	$111.50
Purchase #3	$245.66	7.572%	$264.2614	$264.26	$264.25	$264.30
Purchase #4	$52.49	7.740%	$56.5527	$56.55	$56.55	$56.60
Purchase #5	$154.88	11.854%	$173.2395	$173.24	$173.25	$173.20
Purchase #6	$97.89	4.376%	$102.1737	$102.17	$102.15	$102.20
Purchase #7	$244.36	7.457%	$262.5819	$262.58	$262.60	$262.60
7 purchase totals =	$994.58		$1,078.1202	$1,078.12	$1,078.10	$1,078.20