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	$59.91	3.670%	$62.1087	$62.11	$62.10	$62.10
Purchase #2	$86.94	12.816%	$98.0822	$98.08	$98.10	$98.10
Purchase #3	$101.70	9.372%	$111.2313	$111.23	$111.25	$111.20
Purchase #4	$78.55	13.379%	$89.0592	$89.06	$89.05	$89.10
Purchase #5	$234.81	7.558%	$252.5569	$252.56	$252.55	$252.60
Purchase #6	$83.99	8.808%	$91.3878	$91.39	$91.40	$91.40
Purchase #7	$158.43	9.464%	$173.4238	$173.42	$173.40	$173.40
7 purchase totals =	$804.33		$877.8499	$877.85	$877.85	$877.90