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	$217.26	9.619%	$238.1582	$238.16	$238.15	$238.20
Purchase #2	$204.59	4.738%	$214.2835	$214.28	$214.30	$214.30
Purchase #3	$165.90	6.359%	$176.4496	$176.45	$176.45	$176.40
Purchase #4	$245.75	5.193%	$258.5118	$258.51	$258.50	$258.50
Purchase #5	$173.89	7.726%	$187.3247	$187.32	$187.30	$187.30
Purchase #6	$164.45	5.295%	$173.1576	$173.16	$173.15	$173.20
Purchase #7	$126.46	4.231%	$131.8105	$131.81	$131.80	$131.80
7 purchase totals =	$1,298.30		$1,379.6959	$1,379.69	$1,379.65	$1,379.70