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	$75.72	7.832%	$81.6504	$81.65	$81.65	$81.70
Purchase #2	$107.50	10.302%	$118.5747	$118.57	$118.55	$118.60
Purchase #3	$176.59	3.329%	$182.4687	$182.47	$182.45	$182.50
Purchase #4	$84.31	9.784%	$92.5589	$92.56	$92.55	$92.60
Purchase #5	$208.30	3.184%	$214.9323	$214.93	$214.95	$214.90
Purchase #6	$69.59	12.162%	$78.0535	$78.05	$78.05	$78.10
Purchase #7	$42.77	6.607%	$45.5958	$45.60	$45.60	$45.60
7 purchase totals =	$764.78		$813.8343	$813.83	$813.80	$814.00