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	$31.26	13.555%	$35.4973	$35.50	$35.50	$35.50
Purchase #2	$167.89	4.348%	$175.1899	$175.19	$175.20	$175.20
Purchase #3	$142.45	4.482%	$148.8346	$148.83	$148.85	$148.80
Purchase #4	$121.42	5.661%	$128.2936	$128.29	$128.30	$128.30
Purchase #5	$247.25	11.285%	$275.1522	$275.15	$275.15	$275.20
Purchase #6	$241.80	6.244%	$256.898	$256.90	$256.90	$256.90
Purchase #7	$249.72	11.593%	$278.67	$278.67	$278.65	$278.70
7 purchase totals =	$1,201.79		$1,298.5356	$1,298.53	$1,298.55	$1,298.60