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	$132.91	13.613%	$151.003	$151.00	$151.00	$151.00
Purchase #2	$174.74	12.670%	$196.8796	$196.88	$196.90	$196.90
Purchase #3	$160.51	12.798%	$181.0521	$181.05	$181.05	$181.10
Purchase #4	$220.89	3.401%	$228.4025	$228.40	$228.40	$228.40
Purchase #5	$176.76	7.133%	$189.3683	$189.37	$189.35	$189.40
Purchase #6	$18.32	4.164%	$19.0828	$19.08	$19.10	$19.10
Purchase #7	$236.75	11.342%	$263.6022	$263.60	$263.60	$263.60
7 purchase totals =	$1,120.88		$1,229.3905	$1,229.38	$1,229.40	$1,229.50