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	$72.49	11.212%	$80.6176	$80.62	$80.60	$80.60
Purchase #2	$177.65	10.843%	$196.9126	$196.91	$196.90	$196.90
Purchase #3	$179.80	3.213%	$185.577	$185.58	$185.60	$185.60
Purchase #4	$126.98	3.114%	$130.9342	$130.93	$130.95	$130.90
Purchase #5	$235.99	11.325%	$262.7159	$262.72	$262.70	$262.70
Purchase #6	$166.79	13.670%	$189.5902	$189.59	$189.60	$189.60
Purchase #7	$139.25	7.777%	$150.0795	$150.08	$150.10	$150.10
7 purchase totals =	$1,098.95		$1,196.4270	$1,196.43	$1,196.45	$1,196.40