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	$204.78	5.550%	$216.1453	$216.15	$216.15	$216.10
Purchase #2	$81.59	9.686%	$89.4928	$89.49	$89.50	$89.50
Purchase #3	$145.95	7.666%	$157.1385	$157.14	$157.15	$157.10
Purchase #4	$29.27	12.868%	$33.0365	$33.04	$33.05	$33.00
Purchase #5	$56.94	10.504%	$62.921	$62.92	$62.90	$62.90
Purchase #6	$74.89	9.857%	$82.2719	$82.27	$82.25	$82.30
Purchase #7	$75.38	3.651%	$78.1321	$78.13	$78.15	$78.10
7 purchase totals =	$668.80		$719.1381	$719.14	$719.15	$719.00