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	$21.72	9.793%	$23.847	$23.85	$23.85	$23.80
Purchase #2	$81.68	4.651%	$85.4789	$85.48	$85.50	$85.50
Purchase #3	$14.46	4.557%	$15.1189	$15.12	$15.10	$15.10
Purchase #4	$19.82	6.624%	$21.1329	$21.13	$21.15	$21.10
Purchase #5	$136.81	10.187%	$150.7468	$150.75	$150.75	$150.70
Purchase #6	$141.44	7.642%	$152.2488	$152.25	$152.25	$152.20
Purchase #7	$17.82	5.321%	$18.7682	$18.77	$18.75	$18.80
7 purchase totals =	$433.75		$467.3415	$467.35	$467.35	$467.20