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	$128.91	4.572%	$134.8038	$134.80	$134.80	$134.80
Purchase #2	$81.57	9.644%	$89.4366	$89.44	$89.45	$89.40
Purchase #3	$225.55	11.556%	$251.6146	$251.61	$251.60	$251.60
Purchase #4	$141.88	6.700%	$151.386	$151.39	$151.40	$151.40
Purchase #5	$171.44	11.556%	$191.2516	$191.25	$191.25	$191.30
Purchase #6	$244.50	11.693%	$273.0894	$273.09	$273.10	$273.10
Purchase #7	$11.60	8.189%	$12.5499	$12.55	$12.55	$12.50
7 purchase totals =	$1,005.45		$1,104.1319	$1,104.13	$1,104.15	$1,104.10