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	$176.31	4.383%	$184.0377	$184.04	$184.05	$184.00
Purchase #2	$247.79	12.323%	$278.3252	$278.33	$278.35	$278.30
Purchase #3	$63.27	11.666%	$70.6511	$70.65	$70.65	$70.70
Purchase #4	$153.59	12.385%	$172.6121	$172.61	$172.60	$172.60
Purchase #5	$115.34	7.237%	$123.6872	$123.69	$123.70	$123.70
Purchase #6	$29.48	4.622%	$30.8426	$30.84	$30.85	$30.80
Purchase #7	$164.69	13.856%	$187.5094	$187.51	$187.50	$187.50
7 purchase totals =	$950.47		$1,047.6653	$1,047.67	$1,047.70	$1,047.60