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	$152.62	6.328%	$162.2778	$162.28	$162.30	$162.30
Purchase #2	$100.35	11.611%	$112.0016	$112.00	$112.00	$112.00
Purchase #3	$99.51	4.310%	$103.7989	$103.80	$103.80	$103.80
Purchase #4	$145.30	7.477%	$156.1641	$156.16	$156.15	$156.20
Purchase #5	$153.92	7.849%	$166.0012	$166.00	$166.00	$166.00
Purchase #6	$187.33	4.715%	$196.1626	$196.16	$196.15	$196.20
Purchase #7	$245.99	12.361%	$276.3968	$276.40	$276.40	$276.40
7 purchase totals =	$1,085.02		$1,172.8030	$1,172.80	$1,172.80	$1,172.90