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	$184.78	6.579%	$196.9367	$196.94	$196.95	$196.90
Purchase #2	$160.91	8.402%	$174.4297	$174.43	$174.45	$174.40
Purchase #3	$147.95	13.168%	$167.4321	$167.43	$167.45	$167.40
Purchase #4	$65.29	10.569%	$72.1905	$72.19	$72.20	$72.20
Purchase #5	$180.77	7.459%	$194.2536	$194.25	$194.25	$194.30
Purchase #6	$155.87	4.863%	$163.45	$163.45	$163.45	$163.50
Purchase #7	$33.49	7.652%	$36.0527	$36.05	$36.05	$36.10
7 purchase totals =	$929.06		$1,004.7453	$1,004.74	$1,004.80	$1,004.80