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	$78.70	8.603%	$85.4706	$85.47	$85.45	$85.50
Purchase #2	$201.38	8.335%	$218.165	$218.17	$218.15	$218.20
Purchase #3	$72.92	4.744%	$76.3793	$76.38	$76.40	$76.40
Purchase #4	$50.87	10.664%	$56.2948	$56.29	$56.30	$56.30
Purchase #5	$90.28	5.739%	$95.4612	$95.46	$95.45	$95.50
Purchase #6	$143.55	10.286%	$158.3156	$158.32	$158.30	$158.30
Purchase #7	$52.52	12.356%	$59.0094	$59.01	$59.00	$59.00
7 purchase totals =	$690.22		$749.0959	$749.10	$749.05	$749.20