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	$100.58	13.478%	$114.1362	$114.14	$114.15	$114.10
Purchase #2	$29.83	12.197%	$33.4684	$33.47	$33.45	$33.50
Purchase #3	$82.77	11.347%	$92.1619	$92.16	$92.15	$92.20
Purchase #4	$76.93	4.475%	$80.3726	$80.37	$80.35	$80.40
Purchase #5	$54.73	4.404%	$57.1403	$57.14	$57.15	$57.10
Purchase #6	$129.73	10.493%	$143.3426	$143.34	$143.35	$143.30
Purchase #7	$129.87	11.874%	$145.2908	$145.29	$145.30	$145.30
7 purchase totals =	$604.44		$665.9128	$665.91	$665.90	$665.90