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	$209.33	12.382%	$235.2492	$235.25	$235.25	$235.20
Purchase #2	$48.98	6.483%	$52.1554	$52.16	$52.15	$52.20
Purchase #3	$229.50	3.655%	$237.8882	$237.89	$237.90	$237.90
Purchase #4	$27.35	13.534%	$31.0515	$31.05	$31.05	$31.10
Purchase #5	$105.65	5.264%	$111.2114	$111.21	$111.20	$111.20
Purchase #6	$50.26	6.650%	$53.6023	$53.60	$53.60	$53.60
Purchase #7	$173.67	11.376%	$193.4267	$193.43	$193.45	$193.40
7 purchase totals =	$844.74		$914.5847	$914.59	$914.60	$914.60