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	$133.87	5.788%	$141.6184	$141.62	$141.60	$141.60
Purchase #2	$137.48	7.410%	$147.6673	$147.67	$147.65	$147.70
Purchase #3	$25.34	12.598%	$28.5323	$28.53	$28.55	$28.50
Purchase #4	$52.40	13.866%	$59.6658	$59.67	$59.65	$59.70
Purchase #5	$24.39	3.733%	$25.3005	$25.30	$25.30	$25.30
Purchase #6	$229.99	5.174%	$241.8897	$241.89	$241.90	$241.90
Purchase #7	$72.75	13.685%	$82.7058	$82.71	$82.70	$82.70
7 purchase totals =	$676.22		$727.3798	$727.39	$727.35	$727.40