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	$159.51	10.587%	$176.3973	$176.40	$176.40	$176.40
Purchase #2	$191.40	8.698%	$208.048	$208.05	$208.05	$208.00
Purchase #3	$69.93	3.512%	$72.3859	$72.39	$72.40	$72.40
Purchase #4	$132.49	6.112%	$140.5878	$140.59	$140.60	$140.60
Purchase #5	$196.25	11.688%	$219.1877	$219.19	$219.20	$219.20
Purchase #6	$130.65	9.589%	$143.178	$143.18	$143.20	$143.20
Purchase #7	$65.58	9.665%	$71.9183	$71.92	$71.90	$71.90
7 purchase totals =	$945.81		$1,031.7030	$1,031.72	$1,031.75	$1,031.70