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	$232.54	6.827%	$248.4155	$248.42	$248.40	$248.40
Purchase #2	$19.72	8.776%	$21.4506	$21.45	$21.45	$21.50
Purchase #3	$178.49	12.154%	$200.1837	$200.18	$200.20	$200.20
Purchase #4	$54.27	13.641%	$61.673	$61.67	$61.65	$61.70
Purchase #5	$42.50	10.297%	$46.8762	$46.88	$46.90	$46.90
Purchase #6	$207.83	9.744%	$228.081	$228.08	$228.10	$228.10
Purchase #7	$166.92	4.343%	$174.1693	$174.17	$174.15	$174.20
7 purchase totals =	$902.27		$980.8493	$980.85	$980.85	$981.00