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	$50.26	7.262%	$53.9099	$53.91	$53.90	$53.90
Purchase #2	$153.70	13.594%	$174.594	$174.59	$174.60	$174.60
Purchase #3	$240.88	9.359%	$263.424	$263.42	$263.40	$263.40
Purchase #4	$244.55	9.184%	$267.0095	$267.01	$267.00	$267.00
Purchase #5	$207.89	6.615%	$221.6419	$221.64	$221.65	$221.60
Purchase #6	$137.68	9.671%	$150.995	$151.00	$151.00	$151.00
Purchase #7	$189.86	3.486%	$196.4785	$196.48	$196.50	$196.50
7 purchase totals =	$1,224.82		$1,328.0528	$1,328.05	$1,328.05	$1,328.00