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	$186.92	13.350%	$211.8738	$211.87	$211.85	$211.90
Purchase #2	$203.45	11.267%	$226.3727	$226.37	$226.35	$226.40
Purchase #3	$131.42	12.672%	$148.0735	$148.07	$148.05	$148.10
Purchase #4	$54.69	13.191%	$61.9042	$61.90	$61.90	$61.90
Purchase #5	$53.45	4.575%	$55.8953	$55.90	$55.90	$55.90
Purchase #6	$63.72	13.141%	$72.0934	$72.09	$72.10	$72.10
Purchase #7	$236.29	4.540%	$247.0176	$247.02	$247.00	$247.00
7 purchase totals =	$929.94		$1,023.2305	$1,023.22	$1,023.15	$1,023.30