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	$150.50	3.460%	$155.7073	$155.71	$155.70	$155.70
Purchase #2	$164.31	9.481%	$179.8882	$179.89	$179.90	$179.90
Purchase #3	$50.51	4.336%	$52.7001	$52.70	$52.70	$52.70
Purchase #4	$168.75	11.753%	$188.5832	$188.58	$188.60	$188.60
Purchase #5	$200.25	4.261%	$208.7827	$208.78	$208.80	$208.80
Purchase #6	$66.30	11.359%	$73.831	$73.83	$73.85	$73.80
Purchase #7	$203.65	11.115%	$226.2857	$226.29	$226.30	$226.30
7 purchase totals =	$1,004.27		$1,085.7782	$1,085.78	$1,085.85	$1,085.80