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	$169.30	11.136%	$188.1532	$188.15	$188.15	$188.20
Purchase #2	$29.45	13.747%	$33.4985	$33.50	$33.50	$33.50
Purchase #3	$231.95	5.429%	$244.5426	$244.54	$244.55	$244.50
Purchase #4	$93.56	10.427%	$103.3155	$103.32	$103.30	$103.30
Purchase #5	$77.46	8.224%	$83.8303	$83.83	$83.85	$83.80
Purchase #6	$241.75	3.264%	$249.6407	$249.64	$249.65	$249.60
Purchase #7	$28.45	9.589%	$31.1781	$31.18	$31.20	$31.20
7 purchase totals =	$871.92		$934.1589	$934.16	$934.20	$934.10