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	$180.38	8.855%	$196.3526	$196.35	$196.35	$196.40
Purchase #2	$216.88	5.764%	$229.381	$229.38	$229.40	$229.40
Purchase #3	$99.42	5.773%	$105.1595	$105.16	$105.15	$105.20
Purchase #4	$100.37	8.862%	$109.2648	$109.26	$109.25	$109.30
Purchase #5	$117.79	3.224%	$121.5875	$121.59	$121.60	$121.60
Purchase #6	$23.77	6.112%	$25.2228	$25.22	$25.20	$25.20
Purchase #7	$6.62	8.456%	$7.1798	$7.18	$7.20	$7.20
7 purchase totals =	$745.23		$794.1480	$794.14	$794.15	$794.30