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	$134.86	7.479%	$144.9462	$144.95	$144.95	$144.90
Purchase #2	$57.25	11.176%	$63.6483	$63.65	$63.65	$63.60
Purchase #3	$126.63	13.728%	$144.0138	$144.01	$144.00	$144.00
Purchase #4	$114.62	11.449%	$127.7428	$127.74	$127.75	$127.70
Purchase #5	$151.68	5.827%	$160.5184	$160.52	$160.50	$160.50
Purchase #6	$175.94	13.755%	$200.1405	$200.14	$200.15	$200.10
Purchase #7	$242.92	13.518%	$275.7579	$275.76	$275.75	$275.80
7 purchase totals =	$1,003.90		$1,116.7679	$1,116.77	$1,116.75	$1,116.60