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	$43.53	3.469%	$45.0401	$45.04	$45.05	$45.00
Purchase #2	$80.97	10.278%	$89.2921	$89.29	$89.30	$89.30
Purchase #3	$62.69	5.686%	$66.2546	$66.25	$66.25	$66.30
Purchase #4	$111.49	4.298%	$116.2818	$116.28	$116.30	$116.30
Purchase #5	$23.32	3.650%	$24.1712	$24.17	$24.15	$24.20
Purchase #6	$102.90	13.554%	$116.8471	$116.85	$116.85	$116.80
Purchase #7	$147.53	12.575%	$166.0819	$166.08	$166.10	$166.10
7 purchase totals =	$572.43		$623.9688	$623.96	$624.00	$624.00