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	$111.74	10.384%	$123.3431	$123.34	$123.35	$123.30
Purchase #2	$18.64	5.395%	$19.6456	$19.65	$19.65	$19.60
Purchase #3	$93.55	11.771%	$104.5618	$104.56	$104.55	$104.60
Purchase #4	$169.43	13.273%	$191.9184	$191.92	$191.90	$191.90
Purchase #5	$95.55	3.131%	$98.5417	$98.54	$98.55	$98.50
Purchase #6	$14.62	12.443%	$16.4392	$16.44	$16.45	$16.40
Purchase #7	$144.25	10.319%	$159.1352	$159.14	$159.15	$159.10
7 purchase totals =	$647.78		$713.5850	$713.59	$713.60	$713.40