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	$92.88	13.178%	$105.1197	$105.12	$105.10	$105.10
Purchase #2	$199.71	13.386%	$226.4432	$226.44	$226.45	$226.40
Purchase #3	$174.56	5.363%	$183.9217	$183.92	$183.90	$183.90
Purchase #4	$128.76	9.820%	$141.4042	$141.40	$141.40	$141.40
Purchase #5	$42.65	6.860%	$45.5758	$45.58	$45.60	$45.60
Purchase #6	$100.34	10.520%	$110.8958	$110.90	$110.90	$110.90
Purchase #7	$128.37	4.458%	$134.0927	$134.09	$134.10	$134.10
7 purchase totals =	$867.27		$947.4531	$947.45	$947.45	$947.40