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	$142.31	9.380%	$155.6587	$155.66	$155.65	$155.70
Purchase #2	$161.54	4.429%	$168.6946	$168.69	$168.70	$168.70
Purchase #3	$129.66	8.322%	$140.4503	$140.45	$140.45	$140.50
Purchase #4	$131.60	6.151%	$139.6947	$139.69	$139.70	$139.70
Purchase #5	$218.41	3.406%	$225.849	$225.85	$225.85	$225.80
Purchase #6	$61.97	10.174%	$68.2748	$68.27	$68.25	$68.30
Purchase #7	$99.49	12.737%	$112.162	$112.16	$112.15	$112.20
7 purchase totals =	$944.98		$1,010.7841	$1,010.77	$1,010.75	$1,010.90