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	$175.42	3.429%	$181.4352	$181.44	$181.45	$181.40
Purchase #2	$139.56	9.394%	$152.6703	$152.67	$152.65	$152.70
Purchase #3	$247.92	7.159%	$265.6686	$265.67	$265.65	$265.70
Purchase #4	$84.71	5.845%	$89.6613	$89.66	$89.65	$89.70
Purchase #5	$10.27	9.644%	$11.2604	$11.26	$11.25	$11.30
Purchase #6	$188.63	9.173%	$205.933	$205.93	$205.95	$205.90
Purchase #7	$111.60	10.847%	$123.7053	$123.71	$123.70	$123.70
7 purchase totals =	$958.11		$1,030.3341	$1,030.34	$1,030.30	$1,030.40