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	$112.39	13.854%	$127.9605	$127.96	$127.95	$128.00
Purchase #2	$44.85	6.667%	$47.8401	$47.84	$47.85	$47.80
Purchase #3	$183.92	6.640%	$196.1323	$196.13	$196.15	$196.10
Purchase #4	$197.89	8.141%	$214.0002	$214.00	$214.00	$214.00
Purchase #5	$189.95	11.405%	$211.6138	$211.61	$211.60	$211.60
Purchase #6	$34.80	7.469%	$37.3992	$37.40	$37.40	$37.40
Purchase #7	$175.61	8.183%	$189.9802	$189.98	$190.00	$190.00
7 purchase totals =	$939.41		$1,024.9263	$1,024.92	$1,024.95	$1,024.90