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	$9.83	10.330%	$10.8454	$10.85	$10.85	$10.80
Purchase #2	$159.61	13.475%	$181.1174	$181.12	$181.10	$181.10
Purchase #3	$237.65	11.138%	$264.1195	$264.12	$264.10	$264.10
Purchase #4	$227.59	13.782%	$258.9565	$258.96	$258.95	$259.00
Purchase #5	$247.35	10.832%	$274.143	$274.14	$274.15	$274.10
Purchase #6	$69.27	4.720%	$72.5395	$72.54	$72.55	$72.50
Purchase #7	$30.51	9.610%	$33.442	$33.44	$33.45	$33.40
7 purchase totals =	$981.81		$1,095.1633	$1,095.17	$1,095.15	$1,095.00