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	$240.55	6.547%	$256.2988	$256.30	$256.30	$256.30
Purchase #2	$219.99	5.749%	$232.6372	$232.64	$232.65	$232.60
Purchase #3	$139.59	9.191%	$152.4197	$152.42	$152.40	$152.40
Purchase #4	$191.40	9.450%	$209.4873	$209.49	$209.50	$209.50
Purchase #5	$121.71	13.103%	$137.6577	$137.66	$137.65	$137.70
Purchase #6	$79.86	3.418%	$82.5896	$82.59	$82.60	$82.60
Purchase #7	$32.34	7.500%	$34.7655	$34.77	$34.75	$34.80
7 purchase totals =	$1,025.44		$1,105.8558	$1,105.87	$1,105.85	$1,105.90