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	$183.84	6.690%	$196.1389	$196.14	$196.15	$196.10
Purchase #2	$197.69	9.401%	$216.2748	$216.27	$216.25	$216.30
Purchase #3	$108.77	13.146%	$123.0689	$123.07	$123.05	$123.10
Purchase #4	$49.30	3.723%	$51.1354	$51.14	$51.15	$51.10
Purchase #5	$62.62	8.607%	$68.0097	$68.01	$68.00	$68.00
Purchase #6	$153.68	9.236%	$167.8739	$167.87	$167.85	$167.90
Purchase #7	$117.59	8.439%	$127.5134	$127.51	$127.50	$127.50
7 purchase totals =	$873.49		$950.0150	$950.01	$949.95	$950.00