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	$28.95	12.621%	$32.6038	$32.60	$32.60	$32.60
Purchase #2	$81.64	4.319%	$85.166	$85.17	$85.15	$85.20
Purchase #3	$80.55	4.618%	$84.2698	$84.27	$84.25	$84.30
Purchase #4	$95.41	10.394%	$105.3269	$105.33	$105.35	$105.30
Purchase #5	$176.37	13.662%	$200.4657	$200.47	$200.45	$200.50
Purchase #6	$144.45	10.569%	$159.7169	$159.72	$159.70	$159.70
Purchase #7	$168.34	6.742%	$179.6895	$179.69	$179.70	$179.70
7 purchase totals =	$775.71		$847.2386	$847.25	$847.20	$847.30