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	$176.58	6.145%	$187.4308	$187.43	$187.45	$187.40
Purchase #2	$132.85	10.155%	$146.3409	$146.34	$146.35	$146.30
Purchase #3	$95.52	10.748%	$105.7865	$105.79	$105.80	$105.80
Purchase #4	$140.92	10.798%	$156.1365	$156.14	$156.15	$156.10
Purchase #5	$160.80	13.383%	$182.3199	$182.32	$182.30	$182.30
Purchase #6	$192.26	6.473%	$204.705	$204.71	$204.70	$204.70
Purchase #7	$66.92	8.433%	$72.5634	$72.56	$72.55	$72.60
7 purchase totals =	$965.85		$1,055.2830	$1,055.29	$1,055.30	$1,055.20