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	$167.28	12.407%	$188.0344	$188.03	$188.05	$188.00
Purchase #2	$61.40	7.739%	$66.1517	$66.15	$66.15	$66.20
Purchase #3	$106.61	5.810%	$112.804	$112.80	$112.80	$112.80
Purchase #4	$43.39	8.572%	$47.1094	$47.11	$47.10	$47.10
Purchase #5	$186.30	5.382%	$196.3267	$196.33	$196.35	$196.30
Purchase #6	$233.72	5.833%	$247.3529	$247.35	$247.35	$247.40
Purchase #7	$66.64	7.271%	$71.4854	$71.49	$71.50	$71.50
7 purchase totals =	$865.34		$929.2645	$929.26	$929.30	$929.30