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	$189.77	7.773%	$204.5208	$204.52	$204.50	$204.50
Purchase #2	$87.89	11.821%	$98.2795	$98.28	$98.30	$98.30
Purchase #3	$169.86	13.223%	$192.3206	$192.32	$192.30	$192.30
Purchase #4	$126.58	4.523%	$132.3052	$132.31	$132.30	$132.30
Purchase #5	$158.92	3.539%	$164.5442	$164.54	$164.55	$164.50
Purchase #6	$183.92	6.768%	$196.3677	$196.37	$196.35	$196.40
Purchase #7	$127.56	3.592%	$132.142	$132.14	$132.15	$132.10
7 purchase totals =	$1,044.50		$1,120.4800	$1,120.48	$1,120.45	$1,120.40