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	$99.64	11.415%	$111.0139	$111.01	$111.00	$111.00
Purchase #2	$213.48	9.850%	$234.5078	$234.51	$234.50	$234.50
Purchase #3	$103.86	4.588%	$108.6251	$108.63	$108.65	$108.60
Purchase #4	$41.83	11.312%	$46.5618	$46.56	$46.55	$46.60
Purchase #5	$243.25	9.137%	$265.4758	$265.48	$265.50	$265.50
Purchase #6	$107.86	4.826%	$113.0653	$113.07	$113.05	$113.10
Purchase #7	$54.30	11.318%	$60.4457	$60.45	$60.45	$60.40
7 purchase totals =	$864.22		$939.6954	$939.71	$939.70	$939.70