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	$158.68	8.330%	$171.898	$171.90	$171.90	$171.90
Purchase #2	$82.71	8.420%	$89.6742	$89.67	$89.65	$89.70
Purchase #3	$140.90	9.675%	$154.5321	$154.53	$154.55	$154.50
Purchase #4	$89.95	13.329%	$101.9394	$101.94	$101.95	$101.90
Purchase #5	$153.83	3.846%	$159.7463	$159.75	$159.75	$159.70
Purchase #6	$96.32	12.373%	$108.2377	$108.24	$108.25	$108.20
Purchase #7	$233.95	9.441%	$256.0372	$256.04	$256.05	$256.00
7 purchase totals =	$956.34		$1,042.0649	$1,042.07	$1,042.10	$1,041.90