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	$107.48	11.583%	$119.9294	$119.93	$119.95	$119.90
Purchase #2	$177.39	4.392%	$185.181	$185.18	$185.20	$185.20
Purchase #3	$152.55	5.636%	$161.1477	$161.15	$161.15	$161.10
Purchase #4	$73.28	12.726%	$82.6056	$82.61	$82.60	$82.60
Purchase #5	$226.64	6.621%	$241.6458	$241.65	$241.65	$241.60
Purchase #6	$149.81	5.757%	$158.4346	$158.43	$158.45	$158.40
Purchase #7	$45.58	10.687%	$50.4511	$50.45	$50.45	$50.50
7 purchase totals =	$932.73		$999.3952	$999.40	$999.45	$999.30