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	$97.91	11.810%	$109.4732	$109.47	$109.45	$109.50
Purchase #2	$12.99	3.563%	$13.4528	$13.45	$13.45	$13.50
Purchase #3	$132.27	9.254%	$144.5103	$144.51	$144.50	$144.50
Purchase #4	$51.59	12.180%	$57.8737	$57.87	$57.85	$57.90
Purchase #5	$139.46	6.685%	$148.7829	$148.78	$148.80	$148.80
Purchase #6	$43.68	5.816%	$46.2204	$46.22	$46.20	$46.20
Purchase #7	$175.95	9.604%	$192.8482	$192.85	$192.85	$192.80
7 purchase totals =	$653.85		$713.1615	$713.15	$713.10	$713.20