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	$239.83	4.393%	$250.3657	$250.37	$250.35	$250.40
Purchase #2	$72.37	5.652%	$76.4604	$76.46	$76.45	$76.50
Purchase #3	$85.45	13.352%	$96.8593	$96.86	$96.85	$96.90
Purchase #4	$118.51	11.110%	$131.6765	$131.68	$131.70	$131.70
Purchase #5	$183.34	6.240%	$194.7804	$194.78	$194.80	$194.80
Purchase #6	$53.49	6.684%	$57.0653	$57.07	$57.05	$57.10
Purchase #7	$222.25	9.189%	$242.6726	$242.67	$242.65	$242.70
7 purchase totals =	$975.24		$1,049.8802	$1,049.89	$1,049.85	$1,050.10