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	$150.32	3.345%	$155.3482	$155.35	$155.35	$155.30
Purchase #2	$136.95	7.138%	$146.7255	$146.73	$146.75	$146.70
Purchase #3	$163.60	6.833%	$174.7788	$174.78	$174.80	$174.80
Purchase #4	$143.67	6.160%	$152.5201	$152.52	$152.50	$152.50
Purchase #5	$124.85	6.608%	$133.1001	$133.10	$133.10	$133.10
Purchase #6	$117.65	4.808%	$123.3066	$123.31	$123.30	$123.30
Purchase #7	$171.71	5.774%	$181.6245	$181.62	$181.60	$181.60
7 purchase totals =	$1,008.75		$1,067.4038	$1,067.41	$1,067.40	$1,067.30