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	$219.96	9.469%	$240.788	$240.79	$240.80	$240.80
Purchase #2	$40.73	3.176%	$42.0236	$42.02	$42.00	$42.00
Purchase #3	$229.80	8.395%	$249.0917	$249.09	$249.10	$249.10
Purchase #4	$127.31	13.784%	$144.8584	$144.86	$144.85	$144.90
Purchase #5	$55.84	5.874%	$59.12	$59.12	$59.10	$59.10
Purchase #6	$126.46	6.269%	$134.3878	$134.39	$134.40	$134.40
Purchase #7	$99.70	12.345%	$112.008	$112.01	$112.00	$112.00
7 purchase totals =	$899.80		$982.2775	$982.28	$982.25	$982.30