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	$140.76	13.694%	$160.0357	$160.04	$160.05	$160.00
Purchase #2	$243.46	5.666%	$257.2544	$257.25	$257.25	$257.30
Purchase #3	$159.32	12.762%	$179.6524	$179.65	$179.65	$179.70
Purchase #4	$40.55	4.826%	$42.5069	$42.51	$42.50	$42.50
Purchase #5	$140.56	5.610%	$148.4454	$148.45	$148.45	$148.40
Purchase #6	$172.34	9.322%	$188.4055	$188.41	$188.40	$188.40
Purchase #7	$217.83	11.495%	$242.8696	$242.87	$242.85	$242.90
7 purchase totals =	$1,114.82		$1,219.1699	$1,219.18	$1,219.15	$1,219.20