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	$124.82	13.754%	$141.9877	$141.99	$142.00	$142.00
Purchase #2	$234.72	4.520%	$245.3293	$245.33	$245.35	$245.30
Purchase #3	$154.88	11.618%	$172.874	$172.87	$172.85	$172.90
Purchase #4	$70.44	10.817%	$78.0595	$78.06	$78.05	$78.10
Purchase #5	$171.37	5.286%	$180.4286	$180.43	$180.45	$180.40
Purchase #6	$197.92	5.180%	$208.1723	$208.17	$208.15	$208.20
Purchase #7	$160.89	12.650%	$181.2426	$181.24	$181.25	$181.20
7 purchase totals =	$1,115.04		$1,208.0940	$1,208.09	$1,208.10	$1,208.10