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	$176.88	5.409%	$186.4474	$186.45	$186.45	$186.40
Purchase #2	$114.54	11.219%	$127.3902	$127.39	$127.40	$127.40
Purchase #3	$111.65	10.590%	$123.4737	$123.47	$123.45	$123.50
Purchase #4	$215.43	3.118%	$222.1471	$222.15	$222.15	$222.10
Purchase #5	$50.69	12.312%	$56.931	$56.93	$56.95	$56.90
Purchase #6	$240.31	8.482%	$260.6931	$260.69	$260.70	$260.70
Purchase #7	$235.93	4.697%	$247.0116	$247.01	$247.00	$247.00
7 purchase totals =	$1,145.43		$1,224.0941	$1,224.09	$1,224.10	$1,224.00