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	$76.54	12.732%	$86.2851	$86.29	$86.30	$86.30
Purchase #2	$15.59	12.416%	$17.5257	$17.53	$17.55	$17.50
Purchase #3	$42.82	9.623%	$46.9406	$46.94	$46.95	$46.90
Purchase #4	$13.52	7.367%	$14.516	$14.52	$14.50	$14.50
Purchase #5	$9.35	13.383%	$10.6013	$10.60	$10.60	$10.60
Purchase #6	$132.46	13.463%	$150.2931	$150.29	$150.30	$150.30
Purchase #7	$110.62	11.517%	$123.3601	$123.36	$123.35	$123.40
7 purchase totals =	$400.90		$449.5219	$449.53	$449.55	$449.50