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	$229.54	6.495%	$244.4486	$244.45	$244.45	$244.40
Purchase #2	$149.87	3.190%	$154.6509	$154.65	$154.65	$154.70
Purchase #3	$138.46	4.176%	$144.2421	$144.24	$144.25	$144.20
Purchase #4	$72.89	9.287%	$79.6593	$79.66	$79.65	$79.70
Purchase #5	$30.25	13.491%	$34.331	$34.33	$34.35	$34.30
Purchase #6	$208.41	6.695%	$222.363	$222.36	$222.35	$222.40
Purchase #7	$172.60	7.854%	$186.156	$186.16	$186.15	$186.20
7 purchase totals =	$1,002.02		$1,065.8509	$1,065.85	$1,065.85	$1,065.90