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	$43.60	6.534%	$46.4488	$46.45	$46.45	$46.40
Purchase #2	$87.62	7.426%	$94.1267	$94.13	$94.15	$94.10
Purchase #3	$29.34	7.740%	$31.6109	$31.61	$31.60	$31.60
Purchase #4	$237.94	8.860%	$259.0215	$259.02	$259.00	$259.00
Purchase #5	$74.37	6.108%	$78.9125	$78.91	$78.90	$78.90
Purchase #6	$95.90	5.264%	$100.9482	$100.95	$100.95	$100.90
Purchase #7	$158.90	4.552%	$166.1331	$166.13	$166.15	$166.10
7 purchase totals =	$727.67		$777.2017	$777.20	$777.20	$777.00