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	$209.84	8.845%	$228.4003	$228.40	$228.40	$228.40
Purchase #2	$98.94	5.674%	$104.5539	$104.55	$104.55	$104.60
Purchase #3	$74.84	10.839%	$82.9519	$82.95	$82.95	$83.00
Purchase #4	$107.98	9.584%	$118.3288	$118.33	$118.35	$118.30
Purchase #5	$241.25	8.665%	$262.1543	$262.15	$262.15	$262.20
Purchase #6	$131.39	10.303%	$144.9271	$144.93	$144.95	$144.90
Purchase #7	$127.53	9.608%	$139.7831	$139.78	$139.80	$139.80
7 purchase totals =	$991.77		$1,081.0994	$1,081.09	$1,081.15	$1,081.20