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	$112.37	4.322%	$117.2266	$117.23	$117.25	$117.20
Purchase #2	$187.41	3.640%	$194.2317	$194.23	$194.25	$194.20
Purchase #3	$225.70	12.488%	$253.8854	$253.89	$253.90	$253.90
Purchase #4	$28.68	12.544%	$32.2776	$32.28	$32.30	$32.30
Purchase #5	$153.33	4.286%	$159.9017	$159.90	$159.90	$159.90
Purchase #6	$38.99	11.714%	$43.5573	$43.56	$43.55	$43.60
Purchase #7	$61.30	8.433%	$66.4694	$66.47	$66.45	$66.50
7 purchase totals =	$807.78		$867.5497	$867.56	$867.60	$867.60