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	$205.54	4.258%	$214.2919	$214.29	$214.30	$214.30
Purchase #2	$186.68	13.209%	$211.3386	$211.34	$211.35	$211.30
Purchase #3	$35.75	9.700%	$39.2178	$39.22	$39.20	$39.20
Purchase #4	$81.59	13.759%	$92.816	$92.82	$92.80	$92.80
Purchase #5	$77.95	3.280%	$80.5068	$80.51	$80.50	$80.50
Purchase #6	$135.86	9.265%	$148.4474	$148.45	$148.45	$148.40
Purchase #7	$197.59	12.726%	$222.7353	$222.74	$222.75	$222.70
7 purchase totals =	$920.96		$1,009.3538	$1,009.37	$1,009.35	$1,009.20