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	$151.71	13.724%	$172.5307	$172.53	$172.55	$172.50
Purchase #2	$104.97	13.426%	$119.0633	$119.06	$119.05	$119.10
Purchase #3	$48.76	5.655%	$51.5174	$51.52	$51.50	$51.50
Purchase #4	$70.31	12.846%	$79.342	$79.34	$79.35	$79.30
Purchase #5	$179.29	11.552%	$200.0016	$200.00	$200.00	$200.00
Purchase #6	$248.93	12.360%	$279.6977	$279.70	$279.70	$279.70
Purchase #7	$41.55	3.155%	$42.8609	$42.86	$42.85	$42.90
7 purchase totals =	$845.52		$945.0136	$945.01	$945.00	$945.00