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	$117.80	4.535%	$123.1422	$123.14	$123.15	$123.10
Purchase #2	$185.63	13.431%	$210.562	$210.56	$210.55	$210.60
Purchase #3	$113.65	13.259%	$128.7189	$128.72	$128.70	$128.70
Purchase #4	$141.58	3.724%	$146.8524	$146.85	$146.85	$146.90
Purchase #5	$47.77	4.615%	$49.9746	$49.97	$49.95	$50.00
Purchase #6	$173.30	3.429%	$179.2425	$179.24	$179.25	$179.20
Purchase #7	$220.43	3.175%	$227.4287	$227.43	$227.45	$227.40
7 purchase totals =	$1,000.16		$1,065.9213	$1,065.91	$1,065.90	$1,065.90