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	$226.68	12.539%	$255.1034	$255.10	$255.10	$255.10
Purchase #2	$137.35	13.102%	$155.3456	$155.35	$155.35	$155.30
Purchase #3	$45.59	5.264%	$47.9899	$47.99	$48.00	$48.00
Purchase #4	$224.80	13.724%	$255.6516	$255.65	$255.65	$255.70
Purchase #5	$40.47	5.857%	$42.8403	$42.84	$42.85	$42.80
Purchase #6	$183.65	6.736%	$196.0207	$196.02	$196.00	$196.00
Purchase #7	$89.92	3.257%	$92.8487	$92.85	$92.85	$92.80
7 purchase totals =	$948.46		$1,045.8002	$1,045.80	$1,045.80	$1,045.70