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	$64.33	10.734%	$71.2352	$71.24	$71.25	$71.20
Purchase #2	$185.40	5.341%	$195.3022	$195.30	$195.30	$195.30
Purchase #3	$56.40	4.730%	$59.0677	$59.07	$59.05	$59.10
Purchase #4	$226.33	10.269%	$249.5718	$249.57	$249.55	$249.60
Purchase #5	$49.81	9.487%	$54.5355	$54.54	$54.55	$54.50
Purchase #6	$24.47	11.279%	$27.23	$27.23	$27.25	$27.20
Purchase #7	$112.87	4.682%	$118.1546	$118.15	$118.15	$118.20
7 purchase totals =	$719.61		$775.0970	$775.10	$775.10	$775.10