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	$219.52	13.605%	$249.3857	$249.39	$249.40	$249.40
Purchase #2	$137.85	10.491%	$152.3118	$152.31	$152.30	$152.30
Purchase #3	$62.44	6.542%	$66.5248	$66.52	$66.50	$66.50
Purchase #4	$196.95	9.247%	$215.162	$215.16	$215.15	$215.20
Purchase #5	$28.92	13.760%	$32.8994	$32.90	$32.90	$32.90
Purchase #6	$66.88	5.408%	$70.4969	$70.50	$70.50	$70.50
Purchase #7	$230.65	4.293%	$240.5518	$240.55	$240.55	$240.60
7 purchase totals =	$943.21		$1,027.3324	$1,027.33	$1,027.30	$1,027.40