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	$116.95	5.487%	$123.367	$123.37	$123.35	$123.40
Purchase #2	$97.48	8.502%	$105.7677	$105.77	$105.75	$105.80
Purchase #3	$50.30	3.493%	$52.057	$52.06	$52.05	$52.10
Purchase #4	$51.59	6.869%	$55.1337	$55.13	$55.15	$55.10
Purchase #5	$92.95	11.639%	$103.7685	$103.77	$103.75	$103.80
Purchase #6	$38.88	8.770%	$42.2898	$42.29	$42.30	$42.30
Purchase #7	$138.25	9.149%	$150.8985	$150.90	$150.90	$150.90
7 purchase totals =	$586.40		$633.2822	$633.29	$633.25	$633.40