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	$210.65	8.796%	$229.1788	$229.18	$229.20	$229.20
Purchase #2	$23.25	9.681%	$25.5008	$25.50	$25.50	$25.50
Purchase #3	$43.30	5.264%	$45.5793	$45.58	$45.60	$45.60
Purchase #4	$83.71	6.581%	$89.219	$89.22	$89.20	$89.20
Purchase #5	$116.83	13.710%	$132.8474	$132.85	$132.85	$132.80
Purchase #6	$117.70	4.826%	$123.3802	$123.38	$123.40	$123.40
Purchase #7	$212.71	6.150%	$225.7917	$225.79	$225.80	$225.80
7 purchase totals =	$808.15		$871.4972	$871.50	$871.55	$871.50