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	$132.72	7.683%	$142.9169	$142.92	$142.90	$142.90
Purchase #2	$156.92	11.168%	$174.4448	$174.44	$174.45	$174.40
Purchase #3	$183.66	6.873%	$196.283	$196.28	$196.30	$196.30
Purchase #4	$107.39	13.450%	$121.834	$121.83	$121.85	$121.80
Purchase #5	$244.28	7.394%	$262.3421	$262.34	$262.35	$262.30
Purchase #6	$140.66	9.340%	$153.7976	$153.80	$153.80	$153.80
Purchase #7	$111.67	8.105%	$120.7209	$120.72	$120.70	$120.70
7 purchase totals =	$1,077.30		$1,172.3393	$1,172.33	$1,172.35	$1,172.20