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	$47.59	9.446%	$52.0854	$52.09	$52.10	$52.10
Purchase #2	$173.87	13.191%	$196.8052	$196.81	$196.80	$196.80
Purchase #3	$218.92	5.562%	$231.0963	$231.10	$231.10	$231.10
Purchase #4	$123.56	5.326%	$130.1408	$130.14	$130.15	$130.10
Purchase #5	$232.44	9.489%	$254.4962	$254.50	$254.50	$254.50
Purchase #6	$193.55	7.573%	$208.2075	$208.21	$208.20	$208.20
Purchase #7	$101.89	3.622%	$105.5805	$105.58	$105.60	$105.60
7 purchase totals =	$1,091.82		$1,178.4119	$1,178.43	$1,178.45	$1,178.40