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	$226.40	10.549%	$250.2829	$250.28	$250.30	$250.30
Purchase #2	$65.41	7.409%	$70.2562	$70.26	$70.25	$70.30
Purchase #3	$150.71	6.394%	$160.3464	$160.35	$160.35	$160.30
Purchase #4	$183.79	3.634%	$190.4689	$190.47	$190.45	$190.50
Purchase #5	$212.88	9.706%	$233.5421	$233.54	$233.55	$233.50
Purchase #6	$228.94	11.642%	$255.5932	$255.59	$255.60	$255.60
Purchase #7	$13.72	9.540%	$15.0289	$15.03	$15.05	$15.00
7 purchase totals =	$1,081.85		$1,175.5186	$1,175.52	$1,175.55	$1,175.50