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	$69.80	4.149%	$72.696	$72.70	$72.70	$72.70
Purchase #2	$45.32	10.524%	$50.0895	$50.09	$50.10	$50.10
Purchase #3	$126.60	6.475%	$134.7974	$134.80	$134.80	$134.80
Purchase #4	$142.29	9.427%	$155.7037	$155.70	$155.70	$155.70
Purchase #5	$182.56	9.828%	$200.502	$200.50	$200.50	$200.50
Purchase #6	$76.66	7.496%	$82.4064	$82.41	$82.40	$82.40
Purchase #7	$35.83	3.415%	$37.0536	$37.05	$37.05	$37.10
7 purchase totals =	$679.06		$733.2486	$733.25	$733.25	$733.30