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	$63.55	10.246%	$70.0613	$70.06	$70.05	$70.10
Purchase #2	$38.81	4.379%	$40.5095	$40.51	$40.50	$40.50
Purchase #3	$71.51	10.122%	$78.7482	$78.75	$78.75	$78.70
Purchase #4	$109.62	13.725%	$124.6653	$124.67	$124.65	$124.70
Purchase #5	$91.63	3.215%	$94.5759	$94.58	$94.60	$94.60
Purchase #6	$74.38	6.368%	$79.1165	$79.12	$79.10	$79.10
Purchase #7	$176.46	5.149%	$185.5459	$185.55	$185.55	$185.50
7 purchase totals =	$625.96		$673.2226	$673.24	$673.20	$673.20