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	$198.90	8.791%	$216.3853	$216.39	$216.40	$216.40
Purchase #2	$28.46	9.816%	$31.2536	$31.25	$31.25	$31.30
Purchase #3	$58.52	12.701%	$65.9526	$65.95	$65.95	$66.00
Purchase #4	$14.66	6.266%	$15.5786	$15.58	$15.60	$15.60
Purchase #5	$37.78	12.210%	$42.3929	$42.39	$42.40	$42.40
Purchase #6	$119.45	6.469%	$127.1772	$127.18	$127.20	$127.20
Purchase #7	$198.46	12.138%	$222.5491	$222.55	$222.55	$222.50
7 purchase totals =	$656.23		$721.2893	$721.29	$721.35	$721.40