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	$194.45	13.472%	$220.6463	$220.65	$220.65	$220.60
Purchase #2	$224.48	5.362%	$236.5166	$236.52	$236.50	$236.50
Purchase #3	$131.88	11.392%	$146.9038	$146.90	$146.90	$146.90
Purchase #4	$186.50	7.569%	$200.6162	$200.62	$200.60	$200.60
Purchase #5	$96.73	3.845%	$100.4493	$100.45	$100.45	$100.40
Purchase #6	$237.27	13.523%	$269.356	$269.36	$269.35	$269.40
Purchase #7	$82.72	9.522%	$90.5966	$90.60	$90.60	$90.60
7 purchase totals =	$1,154.03		$1,265.0848	$1,265.10	$1,265.05	$1,265.00