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	$188.61	8.695%	$205.0096	$205.01	$205.00	$205.00
Purchase #2	$195.67	7.142%	$209.6448	$209.64	$209.65	$209.60
Purchase #3	$43.42	11.422%	$48.3794	$48.38	$48.40	$48.40
Purchase #4	$22.46	13.389%	$25.4672	$25.47	$25.45	$25.50
Purchase #5	$121.50	5.698%	$128.4231	$128.42	$128.40	$128.40
Purchase #6	$241.77	3.375%	$249.9297	$249.93	$249.95	$249.90
Purchase #7	$137.86	3.209%	$142.2839	$142.28	$142.30	$142.30
7 purchase totals =	$951.29		$1,009.1377	$1,009.13	$1,009.15	$1,009.10