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	$141.90	12.874%	$160.1682	$160.17	$160.15	$160.20
Purchase #2	$173.55	7.536%	$186.6287	$186.63	$186.65	$186.60
Purchase #3	$23.83	3.198%	$24.5921	$24.59	$24.60	$24.60
Purchase #4	$229.52	11.198%	$255.2216	$255.22	$255.20	$255.20
Purchase #5	$222.90	4.870%	$233.7552	$233.76	$233.75	$233.80
Purchase #6	$226.34	12.797%	$255.3047	$255.30	$255.30	$255.30
Purchase #7	$145.67	10.408%	$160.8313	$160.83	$160.85	$160.80
7 purchase totals =	$1,163.71		$1,276.5018	$1,276.50	$1,276.50	$1,276.50