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	$37.74	8.858%	$41.083	$41.08	$41.10	$41.10
Purchase #2	$49.41	13.566%	$56.113	$56.11	$56.10	$56.10
Purchase #3	$205.27	4.797%	$215.1168	$215.12	$215.10	$215.10
Purchase #4	$151.83	9.634%	$166.4573	$166.46	$166.45	$166.50
Purchase #5	$164.78	4.485%	$172.1704	$172.17	$172.15	$172.20
Purchase #6	$234.86	7.780%	$253.1321	$253.13	$253.15	$253.10
Purchase #7	$153.54	11.417%	$171.0697	$171.07	$171.05	$171.10
7 purchase totals =	$997.43		$1,075.1423	$1,075.14	$1,075.10	$1,075.20