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	$238.31	4.657%	$249.4081	$249.41	$249.40	$249.40
Purchase #2	$146.62	3.824%	$152.2267	$152.23	$152.25	$152.20
Purchase #3	$136.42	5.433%	$143.8317	$143.83	$143.85	$143.80
Purchase #4	$99.48	7.652%	$107.0922	$107.09	$107.10	$107.10
Purchase #5	$163.62	13.331%	$185.4322	$185.43	$185.45	$185.40
Purchase #6	$215.96	8.509%	$234.336	$234.34	$234.35	$234.30
Purchase #7	$40.69	7.717%	$43.83	$43.83	$43.85	$43.80
7 purchase totals =	$1,041.10		$1,116.1569	$1,116.16	$1,116.25	$1,116.00