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	$96.37	9.131%	$105.1695	$105.17	$105.15	$105.20
Purchase #2	$208.42	8.554%	$226.2482	$226.25	$226.25	$226.20
Purchase #3	$89.97	11.497%	$100.3139	$100.31	$100.30	$100.30
Purchase #4	$213.65	12.557%	$240.478	$240.48	$240.50	$240.50
Purchase #5	$17.67	6.274%	$18.7786	$18.78	$18.80	$18.80
Purchase #6	$10.43	3.297%	$10.7739	$10.77	$10.75	$10.80
Purchase #7	$49.87	8.567%	$54.1424	$54.14	$54.15	$54.10
7 purchase totals =	$686.38		$755.9045	$755.90	$755.90	$755.90