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	$80.63	11.465%	$89.8742	$89.87	$89.85	$89.90
Purchase #2	$193.77	3.202%	$199.9745	$199.97	$199.95	$200.00
Purchase #3	$165.32	12.161%	$185.4246	$185.42	$185.40	$185.40
Purchase #4	$179.68	3.649%	$186.2365	$186.24	$186.25	$186.20
Purchase #5	$48.78	5.617%	$51.52	$51.52	$51.50	$51.50
Purchase #6	$159.36	9.138%	$173.9223	$173.92	$173.90	$173.90
Purchase #7	$73.75	10.211%	$81.2806	$81.28	$81.30	$81.30
7 purchase totals =	$901.29		$968.2327	$968.22	$968.15	$968.20