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	$97.80	10.715%	$108.2793	$108.28	$108.30	$108.30
Purchase #2	$163.40	12.618%	$184.0178	$184.02	$184.00	$184.00
Purchase #3	$157.85	9.126%	$172.2554	$172.26	$172.25	$172.30
Purchase #4	$172.42	10.248%	$190.0896	$190.09	$190.10	$190.10
Purchase #5	$156.26	6.290%	$166.0888	$166.09	$166.10	$166.10
Purchase #6	$76.96	6.651%	$82.0786	$82.08	$82.10	$82.10
Purchase #7	$144.26	9.804%	$158.4033	$158.40	$158.40	$158.40
7 purchase totals =	$968.95		$1,061.2128	$1,061.22	$1,061.25	$1,061.30