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	$103.97	4.134%	$108.2681	$108.27	$108.25	$108.30
Purchase #2	$102.93	9.309%	$112.5118	$112.51	$112.50	$112.50
Purchase #3	$219.32	5.696%	$231.8125	$231.81	$231.80	$231.80
Purchase #4	$105.31	6.778%	$112.4479	$112.45	$112.45	$112.40
Purchase #5	$41.47	12.511%	$46.6583	$46.66	$46.65	$46.70
Purchase #6	$97.90	13.522%	$111.138	$111.14	$111.15	$111.10
Purchase #7	$208.38	6.684%	$222.3081	$222.31	$222.30	$222.30
7 purchase totals =	$879.28		$945.1447	$945.15	$945.10	$945.10