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	$63.26	11.255%	$70.3799	$70.38	$70.40	$70.40
Purchase #2	$53.69	3.182%	$55.3984	$55.40	$55.40	$55.40
Purchase #3	$204.82	5.624%	$216.3391	$216.34	$216.35	$216.30
Purchase #4	$112.49	13.779%	$127.99	$127.99	$128.00	$128.00
Purchase #5	$156.39	12.289%	$175.6088	$175.61	$175.60	$175.60
Purchase #6	$54.44	8.510%	$59.0728	$59.07	$59.05	$59.10
Purchase #7	$53.42	4.420%	$55.7812	$55.78	$55.80	$55.80
7 purchase totals =	$698.51		$760.5702	$760.57	$760.60	$760.60