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	$167.37	6.839%	$178.8164	$178.82	$178.80	$178.80
Purchase #2	$218.97	11.338%	$243.7968	$243.80	$243.80	$243.80
Purchase #3	$149.66	8.380%	$162.2015	$162.20	$162.20	$162.20
Purchase #4	$72.88	13.691%	$82.858	$82.86	$82.85	$82.90
Purchase #5	$13.46	5.258%	$14.1677	$14.17	$14.15	$14.20
Purchase #6	$80.93	10.685%	$89.5774	$89.58	$89.60	$89.60
Purchase #7	$180.74	3.495%	$187.0569	$187.06	$187.05	$187.10
7 purchase totals =	$884.01		$958.4747	$958.49	$958.45	$958.60