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	$118.28	13.719%	$134.5068	$134.51	$134.50	$134.50
Purchase #2	$83.65	10.626%	$92.5386	$92.54	$92.55	$92.50
Purchase #3	$250.72	6.690%	$267.4932	$267.49	$267.50	$267.50
Purchase #4	$128.89	4.350%	$134.4967	$134.50	$134.50	$134.50
Purchase #5	$115.46	6.874%	$123.3967	$123.40	$123.40	$123.40
Purchase #6	$173.33	5.664%	$183.1474	$183.15	$183.15	$183.10
Purchase #7	$134.38	9.288%	$146.8612	$146.86	$146.85	$146.90
7 purchase totals =	$1,004.71		$1,082.4406	$1,082.45	$1,082.45	$1,082.40