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	$160.31	4.444%	$167.4342	$167.43	$167.45	$167.40
Purchase #2	$89.57	6.225%	$95.1457	$95.15	$95.15	$95.10
Purchase #3	$234.94	8.167%	$254.1275	$254.13	$254.15	$254.10
Purchase #4	$60.93	4.248%	$63.5183	$63.52	$63.50	$63.50
Purchase #5	$74.40	12.829%	$83.9448	$83.94	$83.95	$83.90
Purchase #6	$222.81	7.169%	$238.7832	$238.78	$238.80	$238.80
Purchase #7	$135.75	5.597%	$143.3479	$143.35	$143.35	$143.30
7 purchase totals =	$978.71		$1,046.3016	$1,046.30	$1,046.35	$1,046.10