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	$164.26	8.519%	$178.2533	$178.25	$178.25	$178.30
Purchase #2	$78.79	5.109%	$82.8154	$82.82	$82.80	$82.80
Purchase #3	$40.51	9.518%	$44.3657	$44.37	$44.35	$44.40
Purchase #4	$91.65	7.421%	$98.4513	$98.45	$98.45	$98.50
Purchase #5	$109.52	13.169%	$123.9427	$123.94	$123.95	$123.90
Purchase #6	$217.91	4.863%	$228.507	$228.51	$228.50	$228.50
Purchase #7	$93.70	9.363%	$102.4731	$102.47	$102.45	$102.50
7 purchase totals =	$796.34		$858.8085	$858.81	$858.75	$858.90