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	$138.89	11.287%	$154.5665	$154.57	$154.55	$154.60
Purchase #2	$172.31	5.476%	$181.7457	$181.75	$181.75	$181.70
Purchase #3	$63.85	12.118%	$71.5873	$71.59	$71.60	$71.60
Purchase #4	$192.79	4.110%	$200.7137	$200.71	$200.70	$200.70
Purchase #5	$230.56	4.122%	$240.0637	$240.06	$240.05	$240.10
Purchase #6	$189.64	12.364%	$213.0871	$213.09	$213.10	$213.10
Purchase #7	$160.30	7.485%	$172.2985	$172.30	$172.30	$172.30
7 purchase totals =	$1,148.34		$1,234.0625	$1,234.07	$1,234.05	$1,234.10