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	$148.55	13.140%	$168.0695	$168.07	$168.05	$168.10
Purchase #2	$29.40	6.355%	$31.2684	$31.27	$31.25	$31.30
Purchase #3	$103.41	7.810%	$111.4863	$111.49	$111.50	$111.50
Purchase #4	$227.66	3.635%	$235.9354	$235.94	$235.95	$235.90
Purchase #5	$59.43	4.297%	$61.9837	$61.98	$62.00	$62.00
Purchase #6	$101.29	11.717%	$113.1581	$113.16	$113.15	$113.20
Purchase #7	$186.65	3.770%	$193.6867	$193.69	$193.70	$193.70
7 purchase totals =	$856.39		$915.5881	$915.60	$915.60	$915.70