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	$159.61	8.851%	$173.7371	$173.74	$173.75	$173.70
Purchase #2	$250.46	5.633%	$264.5684	$264.57	$264.55	$264.60
Purchase #3	$136.84	13.312%	$155.0561	$155.06	$155.05	$155.10
Purchase #4	$47.39	9.675%	$51.975	$51.98	$52.00	$52.00
Purchase #5	$200.67	12.357%	$225.4668	$225.47	$225.45	$225.50
Purchase #6	$97.46	7.153%	$104.4313	$104.43	$104.45	$104.40
Purchase #7	$109.42	13.602%	$124.3033	$124.30	$124.30	$124.30
7 purchase totals =	$1,001.85		$1,099.5380	$1,099.55	$1,099.55	$1,099.60