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	$50.59	5.712%	$53.4797	$53.48	$53.50	$53.50
Purchase #2	$158.42	10.842%	$175.5959	$175.60	$175.60	$175.60
Purchase #3	$90.88	4.596%	$95.0568	$95.06	$95.05	$95.10
Purchase #4	$75.89	7.394%	$81.5013	$81.50	$81.50	$81.50
Purchase #5	$56.43	11.156%	$62.7253	$62.73	$62.75	$62.70
Purchase #6	$61.61	7.401%	$66.1698	$66.17	$66.15	$66.20
Purchase #7	$199.56	3.223%	$205.9918	$205.99	$206.00	$206.00
7 purchase totals =	$693.38		$740.5206	$740.53	$740.55	$740.60