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	$167.25	12.215%	$187.6796	$187.68	$187.70	$187.70
Purchase #2	$34.39	9.676%	$37.7176	$37.72	$37.70	$37.70
Purchase #3	$144.71	7.854%	$156.0755	$156.08	$156.10	$156.10
Purchase #4	$152.25	4.442%	$159.0129	$159.01	$159.00	$159.00
Purchase #5	$172.30	6.703%	$183.8493	$183.85	$183.85	$183.80
Purchase #6	$112.98	3.198%	$116.5931	$116.59	$116.60	$116.60
Purchase #7	$41.54	7.319%	$44.5803	$44.58	$44.60	$44.60
7 purchase totals =	$825.42		$885.5083	$885.51	$885.55	$885.50