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	$38.89	12.374%	$43.7022	$43.70	$43.70	$43.70
Purchase #2	$12.33	3.848%	$12.8045	$12.80	$12.80	$12.80
Purchase #3	$27.72	12.344%	$31.1418	$31.14	$31.15	$31.10
Purchase #4	$131.73	6.532%	$140.3346	$140.33	$140.35	$140.30
Purchase #5	$15.82	4.134%	$16.474	$16.47	$16.45	$16.50
Purchase #6	$130.28	11.393%	$145.1228	$145.12	$145.10	$145.10
Purchase #7	$10.98	5.701%	$11.606	$11.61	$11.60	$11.60
7 purchase totals =	$367.75		$401.1859	$401.17	$401.15	$401.10