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	$219.30	9.626%	$240.4098	$240.41	$240.40	$240.40
Purchase #2	$135.84	5.814%	$143.7377	$143.74	$143.75	$143.70
Purchase #3	$82.72	11.829%	$92.5049	$92.50	$92.50	$92.50
Purchase #4	$11.88	13.433%	$13.4758	$13.48	$13.50	$13.50
Purchase #5	$17.87	4.139%	$18.6096	$18.61	$18.60	$18.60
Purchase #6	$211.61	10.323%	$233.4545	$233.45	$233.45	$233.50
Purchase #7	$56.51	5.583%	$59.665	$59.67	$59.65	$59.70
7 purchase totals =	$735.73		$801.8573	$801.86	$801.85	$801.90