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	$65.53	10.857%	$72.6446	$72.64	$72.65	$72.60
Purchase #2	$183.69	6.422%	$195.4866	$195.49	$195.50	$195.50
Purchase #3	$10.46	12.126%	$11.7284	$11.73	$11.75	$11.70
Purchase #4	$141.85	13.252%	$160.648	$160.65	$160.65	$160.60
Purchase #5	$95.77	7.855%	$103.2927	$103.29	$103.30	$103.30
Purchase #6	$79.89	3.794%	$82.921	$82.92	$82.90	$82.90
Purchase #7	$146.88	12.730%	$165.5778	$165.58	$165.60	$165.60
7 purchase totals =	$724.07		$792.2991	$792.30	$792.35	$792.20