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	$160.37	5.716%	$169.5367	$169.54	$169.55	$169.50
Purchase #2	$201.89	8.540%	$219.1314	$219.13	$219.15	$219.10
Purchase #3	$39.60	4.831%	$41.5131	$41.51	$41.50	$41.50
Purchase #4	$109.40	7.874%	$118.0142	$118.01	$118.00	$118.00
Purchase #5	$111.30	6.451%	$118.48	$118.48	$118.50	$118.50
Purchase #6	$108.34	6.603%	$115.4937	$115.49	$115.50	$115.50
Purchase #7	$123.78	12.824%	$139.6535	$139.65	$139.65	$139.70
7 purchase totals =	$854.68		$921.8226	$921.81	$921.85	$921.80