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	$173.52	12.653%	$195.4755	$195.48	$195.50	$195.50
Purchase #2	$112.98	9.473%	$123.6826	$123.68	$123.70	$123.70
Purchase #3	$222.79	3.510%	$230.6099	$230.61	$230.60	$230.60
Purchase #4	$180.49	9.119%	$196.9489	$196.95	$196.95	$196.90
Purchase #5	$119.25	7.214%	$127.8527	$127.85	$127.85	$127.90
Purchase #6	$16.89	8.542%	$18.3327	$18.33	$18.35	$18.30
Purchase #7	$215.44	13.300%	$244.0935	$244.09	$244.10	$244.10
7 purchase totals =	$1,041.36		$1,136.9958	$1,136.99	$1,137.05	$1,137.00