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	$227.37	11.340%	$253.1538	$253.15	$253.15	$253.20
Purchase #2	$94.60	10.690%	$104.7127	$104.71	$104.70	$104.70
Purchase #3	$173.27	4.504%	$181.0741	$181.07	$181.05	$181.10
Purchase #4	$127.54	9.724%	$139.942	$139.94	$139.95	$139.90
Purchase #5	$45.83	11.654%	$51.171	$51.17	$51.15	$51.20
Purchase #6	$152.66	7.851%	$164.6453	$164.65	$164.65	$164.60
Purchase #7	$47.76	12.409%	$53.6865	$53.69	$53.70	$53.70
7 purchase totals =	$869.03		$948.3854	$948.38	$948.35	$948.40