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	$29.72	11.506%	$33.1396	$33.14	$33.15	$33.10
Purchase #2	$216.60	6.730%	$231.1772	$231.18	$231.20	$231.20
Purchase #3	$67.67	6.446%	$72.032	$72.03	$72.05	$72.00
Purchase #4	$54.34	3.495%	$56.2392	$56.24	$56.25	$56.20
Purchase #5	$100.58	3.179%	$103.7774	$103.78	$103.80	$103.80
Purchase #6	$122.61	12.768%	$138.2648	$138.26	$138.25	$138.30
Purchase #7	$174.62	3.131%	$180.0874	$180.09	$180.10	$180.10
7 purchase totals =	$766.14		$814.7176	$814.72	$814.80	$814.70