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	$79.31	5.624%	$83.7704	$83.77	$83.75	$83.80
Purchase #2	$19.67	6.263%	$20.9019	$20.90	$20.90	$20.90
Purchase #3	$75.35	4.235%	$78.5411	$78.54	$78.55	$78.50
Purchase #4	$70.28	12.305%	$78.928	$78.93	$78.95	$78.90
Purchase #5	$48.43	10.487%	$53.5089	$53.51	$53.50	$53.50
Purchase #6	$214.61	5.203%	$225.7762	$225.78	$225.80	$225.80
Purchase #7	$20.52	11.433%	$22.8661	$22.87	$22.85	$22.90
7 purchase totals =	$528.17		$564.2926	$564.30	$564.30	$564.30