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	$199.95	9.799%	$219.5431	$219.54	$219.55	$219.50
Purchase #2	$14.32	13.763%	$16.2909	$16.29	$16.30	$16.30
Purchase #3	$102.98	11.369%	$114.6878	$114.69	$114.70	$114.70
Purchase #4	$46.40	12.782%	$52.3308	$52.33	$52.35	$52.30
Purchase #5	$82.96	7.781%	$89.4151	$89.42	$89.40	$89.40
Purchase #6	$157.52	10.367%	$173.8501	$173.85	$173.85	$173.90
Purchase #7	$242.26	6.698%	$258.4866	$258.49	$258.50	$258.50
7 purchase totals =	$846.39		$924.6044	$924.61	$924.65	$924.60