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	$219.47	12.777%	$247.5117	$247.51	$247.50	$247.50
Purchase #2	$151.40	5.396%	$159.5695	$159.57	$159.55	$159.60
Purchase #3	$151.68	10.515%	$167.6292	$167.63	$167.65	$167.60
Purchase #4	$52.45	13.513%	$59.5376	$59.54	$59.55	$59.50
Purchase #5	$197.54	6.522%	$210.4236	$210.42	$210.40	$210.40
Purchase #6	$107.30	8.470%	$116.3883	$116.39	$116.40	$116.40
Purchase #7	$193.80	5.459%	$204.3795	$204.38	$204.40	$204.40
7 purchase totals =	$1,073.64		$1,165.4394	$1,165.44	$1,165.45	$1,165.40