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	$189.94	12.676%	$214.0168	$214.02	$214.00	$214.00
Purchase #2	$18.28	10.808%	$20.2557	$20.26	$20.25	$20.30
Purchase #3	$246.44	12.528%	$277.314	$277.31	$277.30	$277.30
Purchase #4	$32.85	13.436%	$37.2637	$37.26	$37.25	$37.30
Purchase #5	$54.29	8.709%	$59.0181	$59.02	$59.00	$59.00
Purchase #6	$100.99	11.713%	$112.819	$112.82	$112.80	$112.80
Purchase #7	$166.63	7.687%	$179.4388	$179.44	$179.45	$179.40
7 purchase totals =	$809.42		$900.1261	$900.13	$900.05	$900.10