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	$41.67	8.771%	$45.3249	$45.32	$45.30	$45.30
Purchase #2	$144.29	4.295%	$150.4873	$150.49	$150.50	$150.50
Purchase #3	$105.45	5.665%	$111.4237	$111.42	$111.40	$111.40
Purchase #4	$69.53	4.468%	$72.6366	$72.64	$72.65	$72.60
Purchase #5	$168.60	13.373%	$191.1469	$191.15	$191.15	$191.10
Purchase #6	$201.27	3.718%	$208.7532	$208.75	$208.75	$208.80
Purchase #7	$35.43	10.854%	$39.2756	$39.28	$39.30	$39.30
7 purchase totals =	$766.24		$819.0482	$819.05	$819.05	$819.00