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	$142.88	5.844%	$151.2299	$151.23	$151.25	$151.20
Purchase #2	$212.93	6.417%	$226.5937	$226.59	$226.60	$226.60
Purchase #3	$197.85	12.620%	$222.8187	$222.82	$222.80	$222.80
Purchase #4	$177.35	4.698%	$185.6819	$185.68	$185.70	$185.70
Purchase #5	$40.97	3.672%	$42.4744	$42.47	$42.45	$42.50
Purchase #6	$41.71	7.608%	$44.8833	$44.88	$44.90	$44.90
Purchase #7	$192.64	11.236%	$214.285	$214.29	$214.30	$214.30
7 purchase totals =	$1,006.33		$1,087.9669	$1,087.96	$1,088.00	$1,088.00