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	$152.88	13.679%	$173.7925	$173.79	$173.80	$173.80
Purchase #2	$66.81	12.701%	$75.2955	$75.30	$75.30	$75.30
Purchase #3	$51.34	5.720%	$54.2766	$54.28	$54.30	$54.30
Purchase #4	$234.48	8.862%	$255.2596	$255.26	$255.25	$255.30
Purchase #5	$129.35	13.274%	$146.5199	$146.52	$146.50	$146.50
Purchase #6	$129.45	4.223%	$134.9167	$134.92	$134.90	$134.90
Purchase #7	$193.70	11.164%	$215.3247	$215.32	$215.30	$215.30
7 purchase totals =	$958.01		$1,055.3855	$1,055.39	$1,055.35	$1,055.40