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	$199.50	9.417%	$218.2869	$218.29	$218.30	$218.30
Purchase #2	$52.42	9.429%	$57.3627	$57.36	$57.35	$57.40
Purchase #3	$112.43	6.478%	$119.7132	$119.71	$119.70	$119.70
Purchase #4	$92.30	9.281%	$100.8664	$100.87	$100.85	$100.90
Purchase #5	$214.38	3.775%	$222.4728	$222.47	$222.45	$222.50
Purchase #6	$231.85	11.750%	$259.0924	$259.09	$259.10	$259.10
Purchase #7	$115.87	5.531%	$122.2788	$122.28	$122.30	$122.30
7 purchase totals =	$1,018.75		$1,100.0732	$1,100.07	$1,100.05	$1,100.20