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	$43.61	3.292%	$45.0456	$45.05	$45.05	$45.00
Purchase #2	$145.60	3.791%	$151.1197	$151.12	$151.10	$151.10
Purchase #3	$63.79	11.176%	$70.9192	$70.92	$70.90	$70.90
Purchase #4	$117.68	8.515%	$127.7005	$127.70	$127.70	$127.70
Purchase #5	$205.77	9.306%	$224.919	$224.92	$224.90	$224.90
Purchase #6	$77.75	9.770%	$85.3462	$85.35	$85.35	$85.30
Purchase #7	$55.42	10.549%	$61.2663	$61.27	$61.25	$61.30
7 purchase totals =	$709.62		$766.3165	$766.33	$766.25	$766.20