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	$41.62	9.513%	$45.5793	$45.58	$45.60	$45.60
Purchase #2	$231.65	3.833%	$240.5291	$240.53	$240.55	$240.50
Purchase #3	$59.26	12.727%	$66.802	$66.80	$66.80	$66.80
Purchase #4	$140.44	13.196%	$158.9725	$158.97	$158.95	$159.00
Purchase #5	$129.58	10.589%	$143.3012	$143.30	$143.30	$143.30
Purchase #6	$65.81	13.781%	$74.8793	$74.88	$74.90	$74.90
Purchase #7	$43.91	3.753%	$45.5579	$45.56	$45.55	$45.60
7 purchase totals =	$712.27		$775.6213	$775.62	$775.65	$775.70