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	$200.99	5.204%	$211.4495	$211.45	$211.45	$211.40
Purchase #2	$94.68	9.730%	$103.8924	$103.89	$103.90	$103.90
Purchase #3	$159.55	5.223%	$167.8833	$167.88	$167.90	$167.90
Purchase #4	$99.79	11.300%	$111.0663	$111.07	$111.05	$111.10
Purchase #5	$104.31	8.538%	$113.216	$113.22	$113.20	$113.20
Purchase #6	$107.41	4.176%	$111.8954	$111.90	$111.90	$111.90
Purchase #7	$26.37	6.495%	$28.0827	$28.08	$28.10	$28.10
7 purchase totals =	$793.10		$847.4856	$847.49	$847.50	$847.50