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	$112.86	9.743%	$123.8559	$123.86	$123.85	$123.90
Purchase #2	$104.38	12.399%	$117.3221	$117.32	$117.30	$117.30
Purchase #3	$153.99	3.791%	$159.8278	$159.83	$159.85	$159.80
Purchase #4	$69.47	5.458%	$73.2617	$73.26	$73.25	$73.30
Purchase #5	$60.65	8.676%	$65.912	$65.91	$65.90	$65.90
Purchase #6	$135.72	6.439%	$144.459	$144.46	$144.45	$144.50
Purchase #7	$40.73	10.495%	$45.0046	$45.00	$45.00	$45.00
7 purchase totals =	$677.80		$729.6431	$729.64	$729.60	$729.70