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	$96.70	8.753%	$105.1642	$105.16	$105.15	$105.20
Purchase #2	$112.81	9.869%	$123.9432	$123.94	$123.95	$123.90
Purchase #3	$93.63	10.151%	$103.1344	$103.13	$103.15	$103.10
Purchase #4	$27.95	4.374%	$29.1725	$29.17	$29.15	$29.20
Purchase #5	$136.85	11.782%	$152.9737	$152.97	$152.95	$153.00
Purchase #6	$67.35	12.336%	$75.6583	$75.66	$75.65	$75.70
Purchase #7	$34.51	7.636%	$37.1452	$37.15	$37.15	$37.10
7 purchase totals =	$569.80		$627.1915	$627.18	$627.15	$627.20