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	$248.49	3.475%	$257.125	$257.13	$257.15	$257.10
Purchase #2	$57.30	11.474%	$63.8746	$63.87	$63.85	$63.90
Purchase #3	$167.61	10.422%	$185.0783	$185.08	$185.10	$185.10
Purchase #4	$196.29	13.236%	$222.2709	$222.27	$222.25	$222.30
Purchase #5	$152.68	13.139%	$172.7406	$172.74	$172.75	$172.70
Purchase #6	$100.80	5.581%	$106.4256	$106.43	$106.45	$106.40
Purchase #7	$63.47	6.806%	$67.7898	$67.79	$67.80	$67.80
7 purchase totals =	$986.64		$1,075.3048	$1,075.31	$1,075.35	$1,075.30