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	$127.29	3.408%	$131.628	$131.63	$131.65	$131.60
Purchase #2	$153.28	6.788%	$163.6846	$163.68	$163.70	$163.70
Purchase #3	$177.94	4.343%	$185.6679	$185.67	$185.65	$185.70
Purchase #4	$145.74	12.865%	$164.4895	$164.49	$164.50	$164.50
Purchase #5	$73.52	11.703%	$82.124	$82.12	$82.10	$82.10
Purchase #6	$236.28	13.254%	$267.5966	$267.60	$267.60	$267.60
Purchase #7	$11.83	3.825%	$12.2825	$12.28	$12.30	$12.30
7 purchase totals =	$925.88		$1,007.4731	$1,007.47	$1,007.50	$1,007.50