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	$229.73	4.483%	$240.0288	$240.03	$240.05	$240.00
Purchase #2	$144.27	4.208%	$150.3409	$150.34	$150.35	$150.30
Purchase #3	$157.73	11.105%	$175.2459	$175.25	$175.25	$175.20
Purchase #4	$118.69	8.285%	$128.5235	$128.52	$128.50	$128.50
Purchase #5	$217.56	9.680%	$238.6198	$238.62	$238.60	$238.60
Purchase #6	$15.69	3.235%	$16.1976	$16.20	$16.20	$16.20
Purchase #7	$95.29	5.344%	$100.3823	$100.38	$100.40	$100.40
7 purchase totals =	$978.96		$1,049.3388	$1,049.34	$1,049.35	$1,049.20