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	$157.69	8.667%	$171.357	$171.36	$171.35	$171.40
Purchase #2	$34.85	7.163%	$37.3463	$37.35	$37.35	$37.30
Purchase #3	$185.60	3.307%	$191.7378	$191.74	$191.75	$191.70
Purchase #4	$139.34	11.724%	$155.6762	$155.68	$155.70	$155.70
Purchase #5	$214.77	10.128%	$236.5219	$236.52	$236.50	$236.50
Purchase #6	$149.26	12.848%	$168.4369	$168.44	$168.45	$168.40
Purchase #7	$69.55	12.207%	$78.04	$78.04	$78.05	$78.00
7 purchase totals =	$951.06		$1,039.1161	$1,039.13	$1,039.15	$1,039.00