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	$34.50	11.826%	$38.58	$38.58	$38.60	$38.60
Purchase #2	$55.69	5.224%	$58.5992	$58.60	$58.60	$58.60
Purchase #3	$38.59	8.522%	$41.8786	$41.88	$41.90	$41.90
Purchase #4	$74.72	9.874%	$82.0979	$82.10	$82.10	$82.10
Purchase #5	$56.53	8.404%	$61.2808	$61.28	$61.30	$61.30
Purchase #6	$80.81	5.394%	$85.1689	$85.17	$85.15	$85.20
Purchase #7	$11.91	10.182%	$13.1227	$13.12	$13.10	$13.10
7 purchase totals =	$352.75		$380.7281	$380.73	$380.75	$380.80