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	$225.55	3.505%	$233.4555	$233.46	$233.45	$233.50
Purchase #2	$172.48	10.564%	$190.7008	$190.70	$190.70	$190.70
Purchase #3	$24.65	13.615%	$28.0061	$28.01	$28.00	$28.00
Purchase #4	$101.32	10.228%	$111.683	$111.68	$111.70	$111.70
Purchase #5	$158.36	4.258%	$165.103	$165.10	$165.10	$165.10
Purchase #6	$193.70	11.320%	$215.6268	$215.63	$215.65	$215.60
Purchase #7	$79.32	9.261%	$86.6658	$86.67	$86.65	$86.70
7 purchase totals =	$955.38		$1,031.2410	$1,031.25	$1,031.25	$1,031.30