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	$125.64	13.449%	$142.5373	$142.54	$142.55	$142.50
Purchase #2	$243.30	5.258%	$256.0927	$256.09	$256.10	$256.10
Purchase #3	$110.70	12.622%	$124.6726	$124.67	$124.65	$124.70
Purchase #4	$47.86	7.197%	$51.3045	$51.30	$51.30	$51.30
Purchase #5	$166.52	11.379%	$185.4683	$185.47	$185.45	$185.50
Purchase #6	$168.98	7.127%	$181.0232	$181.02	$181.00	$181.00
Purchase #7	$165.32	4.324%	$172.4684	$172.47	$172.45	$172.50
7 purchase totals =	$1,028.32		$1,113.5670	$1,113.56	$1,113.50	$1,113.60