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	$201.44	9.161%	$219.8939	$219.89	$219.90	$219.90
Purchase #2	$248.44	11.705%	$277.5199	$277.52	$277.50	$277.50
Purchase #3	$247.40	5.120%	$260.0669	$260.07	$260.05	$260.10
Purchase #4	$241.28	6.472%	$256.8956	$256.90	$256.90	$256.90
Purchase #5	$42.51	6.321%	$45.1971	$45.20	$45.20	$45.20
Purchase #6	$82.89	9.122%	$90.4512	$90.45	$90.45	$90.50
Purchase #7	$196.43	11.274%	$218.5755	$218.58	$218.60	$218.60
7 purchase totals =	$1,260.39		$1,368.6001	$1,368.61	$1,368.60	$1,368.70