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	$241.45	5.679%	$255.1619	$255.16	$255.15	$255.20
Purchase #2	$151.98	8.488%	$164.8801	$164.88	$164.90	$164.90
Purchase #3	$99.50	4.444%	$103.9218	$103.92	$103.90	$103.90
Purchase #4	$79.87	8.330%	$86.5232	$86.52	$86.50	$86.50
Purchase #5	$66.59	13.221%	$75.3939	$75.39	$75.40	$75.40
Purchase #6	$142.56	5.520%	$150.4293	$150.43	$150.45	$150.40
Purchase #7	$165.80	4.232%	$172.8167	$172.82	$172.80	$172.80
7 purchase totals =	$947.75		$1,009.1269	$1,009.12	$1,009.10	$1,009.10