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	$72.49	9.335%	$79.2569	$79.26	$79.25	$79.30
Purchase #2	$9.61	13.342%	$10.8922	$10.89	$10.90	$10.90
Purchase #3	$217.81	13.865%	$248.0094	$248.01	$248.00	$248.00
Purchase #4	$59.82	5.768%	$63.2704	$63.27	$63.25	$63.30
Purchase #5	$80.52	13.836%	$91.6607	$91.66	$91.65	$91.70
Purchase #6	$170.34	10.607%	$188.408	$188.41	$188.40	$188.40
Purchase #7	$142.29	6.767%	$151.9188	$151.92	$151.90	$151.90
7 purchase totals =	$752.88		$833.4164	$833.42	$833.35	$833.50