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	$49.68	11.750%	$55.5174	$55.52	$55.50	$55.50
Purchase #2	$222.27	9.574%	$243.5501	$243.55	$243.55	$243.60
Purchase #3	$164.82	6.309%	$175.2185	$175.22	$175.20	$175.20
Purchase #4	$244.34	6.242%	$259.5917	$259.59	$259.60	$259.60
Purchase #5	$77.99	5.560%	$82.3262	$82.33	$82.35	$82.30
Purchase #6	$146.25	3.822%	$151.8397	$151.84	$151.85	$151.80
Purchase #7	$47.29	8.756%	$51.4307	$51.43	$51.45	$51.40
7 purchase totals =	$952.64		$1,019.4743	$1,019.48	$1,019.50	$1,019.40