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	$100.84	4.587%	$105.4655	$105.47	$105.45	$105.50
Purchase #2	$108.42	6.599%	$115.5746	$115.57	$115.55	$115.60
Purchase #3	$33.61	8.647%	$36.5163	$36.52	$36.50	$36.50
Purchase #4	$42.31	8.770%	$46.0206	$46.02	$46.00	$46.00
Purchase #5	$199.29	12.628%	$224.4563	$224.46	$224.45	$224.50
Purchase #6	$75.84	8.746%	$82.473	$82.47	$82.45	$82.50
Purchase #7	$36.67	11.533%	$40.8992	$40.90	$40.90	$40.90
7 purchase totals =	$596.98		$651.4055	$651.41	$651.30	$651.50