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	$117.28	8.407%	$127.1397	$127.14	$127.15	$127.10
Purchase #2	$206.34	9.303%	$225.5358	$225.54	$225.55	$225.50
Purchase #3	$145.99	9.360%	$159.6547	$159.65	$159.65	$159.70
Purchase #4	$152.56	10.176%	$168.0845	$168.08	$168.10	$168.10
Purchase #5	$98.84	13.637%	$112.3188	$112.32	$112.30	$112.30
Purchase #6	$197.72	6.763%	$211.0918	$211.09	$211.10	$211.10
Purchase #7	$127.69	8.413%	$138.4326	$138.43	$138.45	$138.40
7 purchase totals =	$1,046.42		$1,142.2579	$1,142.25	$1,142.30	$1,142.20