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	$225.95	11.859%	$252.7454	$252.75	$252.75	$252.70
Purchase #2	$38.29	10.686%	$42.3817	$42.38	$42.40	$42.40
Purchase #3	$229.45	3.845%	$238.2724	$238.27	$238.25	$238.30
Purchase #4	$109.53	12.504%	$123.2256	$123.23	$123.25	$123.20
Purchase #5	$40.38	13.220%	$45.7182	$45.72	$45.70	$45.70
Purchase #6	$134.56	7.130%	$144.1541	$144.15	$144.15	$144.20
Purchase #7	$181.45	10.345%	$200.221	$200.22	$200.20	$200.20
7 purchase totals =	$959.61		$1,046.7184	$1,046.72	$1,046.70	$1,046.70